Can you catch COVID-19 from Aussie bats? When are you immune? Your questions answered

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Explainer

Can you catch COVID-19 from Aussie bats? When are you immune? Your questions answered

We're answering your questions about COVID-19 as they hit our inboxes, with regular updates featuring at the top of the explainer.

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Since it emerged in China in late 2019, the new coronavirus has infected 5 million people and claimed more than 328,000 lives. To stop a pandemic that spreads from person to person in close quarters, the world has largely shut down. Now parts of it are waking back up with some countries gingerly loosening restrictions while others still suffer the ravages of COVID-19.

As we learn more about the virus, questions from you, our readers, are flooding in. Our explainer team, as well as our health, science and data reporters, will answer as many of them as we can. And when new information comes to light, we'll bring you updates too – with the latest featured up top in this story.

Here's what we know so far.

Bats in Australia don't carry the coronavirus.

Bats in Australia don't carry the coronavirus.Credit: The Age

Can you catch the coronavirus from Australian bats?

The virus behind the pandemic might have genetic roots stretching back to bats in China but in Australia bats won’t give you COVID-19 – it’s not found in any of our wildlife. Still, the virus has fast become a PR disaster for our flying foxes, already hit by a horror six months of food shortages, heatwaves and devastating bushfires.

Animals carry all kinds of coronaviruses, including bats. “Most we’ll never catch, the circumstances have to be just right for a spillover [into humans],” says wildlife disease ecologist Dr Alison Peel. For starters, the virus has to be able to infect humans, as only seven known animal coronaviruses can. Then it needs proximity, Peel notes, such as the cramped conditions of an Asian wet market where wildlife are handled and butchered by people. “Not bats moving in their natural habitat, that’s a completely different scenario,” she says.

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More than 70 per cent of new diseases in humans come from animals – when a virus that has long been circulating in one species jumps into a new host and mutates. These spillovers are happening more and more as people push further into the wild and force animals out of their habitats. Bats, through a lucky quirk of their immune system, carry a host of diseases that do not harm them but their viruses also tend to be fairly stable. That's why, even though this new virus originated in bats, scientists think it likely that it first jumped into another animal (or several), possibly through the wildlife trade, where it morphed into something more potent, able to spread from human to human.

Of course, that doesn’t mean you should touch bats. You can still catch lyssavirus from contact with many Australian species. That rabies-like virus is the only disease known to jump directly from our local bats to people, says director of health and biosecurity at the CSIRO Dr Rob Grenfell. “This is because their original virus genes don’t bind as effectively with our cell’s receptors.”

Bat viruses are only a threat, he says, when our activities push into wildlife habitat. Calls for a cull of the winged mammals by one Victorian Liberal MP have already been dismissed as ridiculous by scientists and Grenfell stresses “culling is not the solution to preventing future spillover events”.

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In fact, some experts say it will have the opposite effect – driving stressed or injured animals to shed more virus and to seek refuge where they are more likely to encounter humans such as in parks, schools and back yards.

“Bats get a bad rap but our forests rely on them,” Peel adds. “Like insects and birds, they’re pollinators but they can actually travel even further than insects or birds.” Experts estimate their service to the global agriculture industry alone is worth billions each year.

In Australia, with so much of our wilderness scorched black by wildfire, bats will be more important than ever to connect the fragmented pockets left standing. Without them, other species such as koalas will be left in even worse shape than they are now, Peel warns. In fact, scientists studying bats say unlocking the secrets of their unique immune system could one day help humans fight diseases of their own.

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Bats mostly keep anti-social hours already – we are each likely to only encounter one or two of the 80 species living in Australia. But, while people often complain of more fruit bats invading the suburbs, picking trees clean and making a racket, the evidence tells a different story. Peel says bats are turning to backyard trees because their own habitats are being cut down, particularly the flowering trees they rely on for food. Overall their numbers are actually falling. "They'd rather be out in the wild," she says. "Bats are protected for a reason, they're in decline and right now [after the bushfires] they're in trouble."

Am I immune after catching COVID-19?

Our immune system has a memory but it's not perfect. Successfully fighting off a virus generally leaves us armed with antibodies ready for round two should it comes back, which usually gives us at least a period of immunity if not always a lifelong shield. But in the case of COVID-19, there are still questions about how many antibodies patients produce – some early studies have found disappointingly low numbers – and how long they might last.

Common coronaviruses such as the ones that give you a cold tend to go away for at a few months or a year before we become susceptible again. Studies of MERS-CoV has found antibodies still present in survivors more than 18 months after recovery, and some survivors of SARS retained antibodies for many years thereafter. An Australian government spokeswoman noted patients with MERS were unlikely to be reinfected shortly after recovery but COVID-19 was still a big question mark.

US infectious disease expert Michael Osterholm has said immunity – and how long it might last – is one of the most important questions confronting us now. Understanding it better would give us an insight into how a vaccine might work or whether we could ever develop herd immunity. So far studies on animals have shown immunity developing after infection, Osterholm says, but there have been no conclusive human tests.

But he notes: "The question is not whether there is immunity, it's how long does it last and how good is it? … I would feel … the weight of the world on all of our shoulders if we found out that this immunity was only very short-lived ... which, at that point, would mean that we're in much more hell of a mess than the US could have imagined in terms of where do we go long-term with vaccine, where do we go with the idea of developing herd immunity. On the other hand, I think we have to be careful not to say that that can't be done. We don't know that yet."

Countries from the UK to Brazil are planning to issue "immunity passports" to recovered COVID-19 patients to help get them back to work and restart local economies, but the World Health Organisation has warned the idea rests on too great an assumption given the evidence void right now. Osterholm agrees: "This is far, far too early in the game to decide that we can do that... [Immunity passports] provide no benefit from a public health standpoint or, for that matter, for the individual ... It's very possible that the information is wrong."

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Still many experts say reports of people appearing to catch this new virus twice are probably best explained by false negative tests clearing them of the infection too early (when the virus had actually remained in their system) rather than catching it a second time. Infectious disease physician Sanjaya Senanayake says the virus collected by the later tests may have been dead or inactive as tests cannot distinguish between viral particles which are infectious and those that have already begun to break down.

Can someone test negative but be a carrier?

Yes. Some people will be infected without symptoms or very mild symptoms. To test for COVID-19 right now, clinicians have two options: the most common method is to take a direct sample of the virus, from a throat or nose swab or in lung phlegm, and examine its genetic code. These tests are considered very accurate but in some cases if they miss the virus – say, because it is further down in the lungs and someone doesn’t cough up any phlegm (or sputum) – they can return a false negative.

Blood tests, which instead look for the body’s immune response to the infection, can also be used though they bring their own false negative risks – antibodies deployed by the body to fight off the virus can take more than a week to form. They may not show up if the test is performed too early into the illness, or they could be mistaken for those used against another virus. This is also true of the rapid finger-prick tests - despite problems overseas with fault tests and concerns about their overal sensitivity, the fast kits are now being rolled out in Australia too though genetic or PCR tests are continuing.

Can you transmit the virus if you have no symptoms?

Yes. One of the big mysteries of the virus is how infectious asymptomatic people really are. Some experts say people shed the most virus when they are unwell, especially while coughing, and the WHO calculates a danger window of infectivity about 48 hours before symptoms first appear – Australia says 24 hours. But other studies have tracked a majority infections in parts of China and Singapore to “stealth” transmitters with mild or no symptoms. Studies out of Italy, Iceland and elsewhere have since shown about 50 per cent of people who tested positive had no symptoms at the time.

This also played out on cruise ship turned floating quarantine site the Diamond Princess in early February. A study found that 50 per cent of those infected didn't show symptoms when they tested positive and, of those, 18 per cent never felt sick at all. Because this virus can spread before symptoms appear, it is especially hard to contain.

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When will I get the 'all clear' for a COVID-19 recovery?

In Australia, if you've had COVID-19 you will have been required to self-isolate. Amid a global shortage of testing kits, only healthcare and aged care workers returning to the frontline will be officially "cleared" with testing (two negative tests) under the national guidelines. Local health authorities keep a close eye on all confirmed cases on the virus in their state and say others may still be retested. But most, such as those recovering in home isolation, only have to meet the following conditions: 10 days have passed since falling ill and symptoms have been gone for 72 hours (usually established via phonecalls).

The US Centre for Disease Control and Prevention advises the same 72-hour window of time after symptoms disappear but some studies overseas have shown the virus can live in the body for weeks after.

The Australian government spokesman said "a small proportion of people may have an illness that has completely resolved but their [tests] remain persistently positive". There a decision on release from isolation will be made on a case-by-case basis after consulting their doctor, the testing lab and the public health unit. The 72-hour rule was decided by the Communicable Diseases Network Australia, which advises Health Minister Greg Hunt, as "a precautionary period to manage uncertainty around how long a confirmed case remains infectious post-symptom resolution", the spokesman said.

"Even in these patients there is uncertainty around whether there is a direct correlation of persistent [positive tests] and infectivity, but what we know from other virus infection, it is not a neat correlation," he said. "There have been case reports of patients testing positive for a couple of weeks post-symptom resolution, but are viral culture negative meaning they are unlikely infectious for very long after symptoms resolve."

When asked again on May 6 about recovery, the government said: "The concern is that there is a risk that these patients might continue to be infectious, but the actual risk is unknown. Patients who are discharged from isolation following recovery from COVID-19 are advised to continue to practise social distancing and enhanced hygiene measures."

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Are there more clusters at meatworks?

In the United States, meat processing plants have become COVID-19 hotspots. In clusters at 115 meat facilities in the US, 5000 workers have fallen ill and 20 people have died, according to the US Centers for Disease Control. One huge pork plant in Sioux Falls, South Dakota accounted, for a time, for almost half the state’s confirmed cases.

With these plants deemed essential to the nation’s food supply, President Donald Trump has now issued an executive order declaring meat processing plants “critical infrastructure” in a bid to have them reopened under federal health and safety guidance, prompting union leaders to warn of forcing workers back without proper protective equipment.

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In Melbourne, meanwhile, more than 60 cases have been linked to an outbreak at a plant in the western suburb of Brooklyn, discovered after a worker went to hospital with an injury and took a COVID-19 test. This is the first case of an Australian meat processing plant reporting COVID-19 cases, says the CEO of the Australian Meat Industry Council, Patrick Hutchinson.

The Melbourne plant’s general manager has said his plant processes all meat in accordance with Australian standards for food safety. And those standards are high. Victoria’s Chief Health Officer, Professor Brett Sutton, says the facility is now closed and does not pose a risk to the community. But is there a connection between meat processing plants and COVID clusters in general?

Meatworks in Australia are extremely tightly regulated, making them an unlikely source of infection, says Michael Grogan, CEO of FGM Consultants, a company that consults for the meatworking industry. The tight regulation is not just because the facilities prepare food for human consumption but because meat workers always face the threat of contracting a disease from an animal they are working with.

“They have uniforms that are laundered at approved premises. You’ve got personal protective equipment that people wear in these areas. There are protective procedures that people have to follow – headwear, hand washing,” he says. “If any particular industry was actually more adapted to washing hands, it would be people in abattoirs.”

Grogan says the workers may have simply shared the virus while sitting together in the break room rather than on the work line.

Brett Sutton says meatworks are particularly vulnerable to outbreaks. “We’ve seen from the US extremely large outbreaks in meatworks, in some ways because they are forced to work closer than some other workplaces,” he said on May 4.

“It might just be the close proximity of workers,” says Professor Catherine Bennett, chair of epidemiology at Deakin University. “And if they are working with more exertion it's possible this increases the likelihood of aerosol spread so it would be harder to manage the required distancing.”

But the meat industry council's Hutchinson says there's nothing inherently infection-prone about meat processing plants. He says in the US there is now particular pressure on meat plants to stay open, as "critical infrastructure", while in the broader community, public health rules have often not been as strictly adhered to as in Australia – meaning workers may catch the virus elsewhere and bring it to a plant. In Australia, he says, the meat industry has doubled down on industry hygiene during the pandemic with nearly three-quarters of council members reporting they temperature tested workers and were banning non-essential visitors to meatworks. The Melbourne meatworks outbreak is an isolated case, he says.

In the United States, a team led by the US Centers for Disease Control looked into the situation at meat or poultry processing facilities in states that reported at least one case of COVID-19 in a plant. In a report released on May 1, it found common factors at meatworks included that it was difficult for workers to maintain physical distancing on production lines; the pace and physical demands of the work made it hard to stick with face masks; and workers were seen covering just their mouths and frequently readjusting their masks. Some workers were incentivised to turn up for shifts when ill. Many workers also lived in crowded conditions and were car-pooling to get to work, increasing their risk of catching the virus outside of work.

Both Food Standards Australia New Zealand and the US Centers for Disease Control (CDC) say there is no evidence to support transmission of COVID-19 associated with food. “It may be possible that a person can get COVID-19 by touching a surface or object, like a packaging container," says the CDC, "that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this is not thought to be the main way the virus spreads.” See how long the virus lasts on surfaces below.

– with Liam Mannix and Tom Cowie

Is it true that COVID-19 causes blood clots?

Doctors are reporting a strange complication from COVID-19 – a small but concerning number of patients are developing blood clots and even having strokes.

In New York City, Australian neurologist Thomas Oxley and his colleagues have just published clinical data on a spike in strokes among younger COVID-19 patients. One woman, 33 and healthy, developed most of the usual COVID-19 symptoms – cough, headache and chills – but after a week, her left arm then her leg went numb. She put off going to hospital for more than a day. On scans, along with the telltale "ground glass" mist of COVID-19 on her lungs, there was a spot deep in her brain – a large-vessel clot blocking an artery. She had had a stroke.

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In the brain of another 44-year-old, a new clot started to form even as Oxley operated to remove the first. Smaller "mini-clots" have also been observed in COVID-19 patients elsewhere overseas, possibly even in their toes, he says.

In Australia, infectious disease physician Sanjaya Senanayake says clotting is one of the main mysteries facing doctors treating COVID-19, although case numbers are low and clots occur mostly in severe cases. Health authorities say the complication hasn’t been seen in Australian patients yet.

"There does seem to be an association with COVID-19," Senanayake says. “We don't know why yet. It's probably a disruption to the clotting mechanism of the blood vessels caused by inflammation ... when the body's immune response kicks in."

The other two dangerous coronaviruses to emerge in the modern era, SARS and MERS, also led to some clotting and stroke, although there was "not a strong association", Senanayake says.

This virus uses the same ACE2 receptor to hack into human cells as SARS, and it is thought to be even better at it, making it more infectious. “ACE2 is also found on the walls of blood vessels,” says Oxley, “so our working theory is that it attacks the vessels and starts an inflammation cascade."

Clotting could also be behind growing reports of heart failure in some COVID-19 patients. But Senanayake says clots could be caused by the virus infecting the heart or something "non-COVID-specific" altogether, more in line with what you would already expect from an intense infection.

Australia’s Deputy Chief Medical Officer, Nick Coatsworth, suggested recently that clots could form in the legs and travel to the lungs in those unwell with sepsis [or] lying in intensive care for a long period. The cause of COVID-19 clotting was still unclear, he said, but Australia was watching cases overseas closely to guide treatment.

Senanayake says advice to consider blood thinners in COVID-19 treatment had already been put out to doctors internationally. At Oxley's hospital, Mount Sinai, internal guidelines now tell staff to put all COVID-19 patients entering intensive care on powerful blood thinners."We're also worried people are missing the early signs of stroke because they're afraid to go to hospital,” he says.

Meanwhile, Melbourne's St Vincent's Hospital will lead a global clinical trial testing a breathable blood thinner to try to prevent clotting in the lungs. The drug Heparin is widely used in hospitals to prevent blood clots and several groups are testing injecting it into patients; uniquely, the St Vincent's trial will test blowing the drug directly into the lungs. The trial was planned for four hospitals in Australia but because we have so few extremely sick patients here, it will be conducted in hospitals in Barcelona, Liverpool and Galway.
– with Liam Mannix

Is the virus mutating into different strains?

Yes and no. Some suggestions that as many as 30 different strains of the virus are already circulating the world, some deadlier than others, have raised concern about the pathogen’s ability to evolve in potency. But while scientists say mutations are happening, these mutations are so far mostly too small to affect the way the virus behaves.

Viruses spread by hijacking our cellular machinery to make copies of themselves. Sometimes they make mistakes – mutations – and sometimes these glitches can transform how the virus operates. But unlike influenza, which regularly throws out mutant strains (and so requires updated vaccinations each season), coronaviruses are more stable – they come with their own proofreading mechanism built in, says Nobel-prizewinning immunologist Professor Peter Doherty.

So far the new virus's mutations are mostly helping scientists track it across the world, tracing outbreaks through variations in its genome as well as patient records.

At the Walter and Eliza Hall Institute in Melbourne, Professor Marc Pellegrini agrees it is unlikely the new virus will mutate fast enough to evade the initial roll-out of a vaccine or treatment. But how long a vaccine remains effective will depend on how stable the virus stays and how the vaccine works against it - the measles virus, for example, mutates fast like the flu but our vaccine still works because the protein it targets in the virus is unaffected by changes.

“Generally, viruses will only mutate [significantly] for a good reason, to get around a roadblock,” Pellegrini says. “If we put out vaccines, that will put pressure on the disease, then there could be random mutations where it tries to jump a roadblock again. Let’s hope not.”

But most researchers, Doherty and Pellegrini among them, think it unlikely the virus will morph into something nastier – by its very nature, a virus wants to spread not kill. “That’s a dead-end for a virus,” Pellegrini says. “It wants us up and about, coughing and sniffling and shedding it. You see viruses like herpes go dormant in a person and then re-emerge so they can keep spreading."

Generally, a virus will beef up its potency to jump across species lines – as this strain likely did when it was first recorded in late 2019. Circulating in a new population over time, it tends to lose more of its bite – as has already happened with swine flu, the 1918 flu and the four most common coronaviruses.

Those four give humans only mild colds and coughs but, as Doherty suggests, "when they first jumped [from animals] into people they probably hit us just as hard as this [virus]”.

Still, a more deadly mutation is not impossible – viruses are driven by the often random process of natural selection, not logic. Sometimes changes will continue to show up by chance or because they help the virus invade new hosts in the short-term. But Doherty adds: “Cancer [which kills regularly] is the stupidest genome in the whole of biology. Apart from in [infectious facial tumours on] Tassie devils, it doesn’t transmit, it commits suicide.”

There's also the theory that the virus could have been circulating in humans for years and "broke out" by evolving into something deadlier in Wuhan. But Pellegrini says that idea doesn't fit with the usual science. And new analysis of the virus's genetic lineage published in the Journal of Infection, Genetics and Evolution on May 5 has since shot it down, finding the virus jumped from animals into humans some time between October and December 2019.

Will the virus hang around like the flu does?

While coronaviruses might be less changeable than other types of viruses, there is still the prospect that, if or when we have a vaccine, COVID-19 could mutate to evade our immunity over time, evolving and lingering each year much like seasonal flu. Most of the world's modelling for how the pandemic might end, including the dreaded second and third waves of rapid infection, are based on what we know about flu.

Scientists hope that because the virus is more stable than the wildly unpredictable influenza, it keep mutating fairly slowly and so be driven out by tough containment measures and a vaccine, if one arrives. The first deadly coronavirus to emerge in the modern era, SARS, was stamped out through aggressive case detection and isolation just nine months after it first emerged but it was also much less infectious than the new virus and had spread to less than 30 countries. Likewise, the other dangerous coronavirus, MERS, is deadlier but harder to catch and so flares up only from time to time.

Given how widespread the virus is already, Pellegrini says it's unlikely to disappear quickly as SARS did. Much will also depend on how long someone is immune naturally after recovering from COVID-19 – scientists are still racing to work that out as early studies yield mixed results.

The possibility of an annual coronavirus season has been suggested by some, including Professor Tony Cunningham who heads up Westmead's Centre for Virus Research and is part of a leading scientific panel now advising the Australian government.

"If this virus had its own way, the pandemic would go on for a very long time," Pellegrini says. "In Australia, we could virtually eliminate it [through containment measures] but we have to open our borders at some stage and the virus will get back in. If we can vaccinate against it, we can change the game."

Achieving "herd immunity" through vaccination (roughly 60 per cent of the population inoculated) will likely still mean small flare-ups of the virus for some time even if it doesn't mutate around our immunity. But it will make a huge difference to the overall shape of the pandemic.

How does weather affect the spread of the virus?

US President Donald Trump offered an optimistic view, back in February, of how the coronavirus pandemic would unfold: “In theory, when it gets a little warmer [the virus] miraculously goes away,” he said. But while viruses tend to break down faster outside the body in warmer temperatures, experts warn this does not mean the northern hemisphere summer will drive out this particular virus.

COVID-19 is new so scientists are looking at similar viruses such as the flu and the more common coronaviruses that cause colds to help them predict how it might behave. These viruses do follow a rough seasonal pattern, peaking over winter. Experts have a number of theories for why this is so – from people crowding together indoors to the effects of the cold, dry air to the natural sterilising powers of the sunlight seen less in winter – and there may not be one single cause.

Here in the southern hemisphere, where the temperatures are only just starting to fall, the timing of COVID-19’s emergence means health authorities in Australia are concerned that caseloads will reach a natural peak alongside our annual winter flu season, causing a crush in hospital wards. That’s why everyone is being urged to have their flu shot and follow tough containment measures that are, so far, “flattening the curve” of Australia’s outbreak. US infectious disease expert Professor Ian Lipkin, who is himself recovering from a case of COVID-19, told ABC radio that the risk was likely to increase in Australia as winter arrived so “it’s going to be very, very important that you stay the course”.

On April 15, a strike force of Australia's top scientists offered rapid advice to government on the question of weather and COVID-19: while the evidence so far shows the virus could spread even in warmer climates, such as in Singapore, the cold weather will likely speed it up further still. But, even if COVID-19 follows the usual seasonal pattern, it is spreading in warm climates right now too so human interventions will play the greatest role in stopping it, they advised. Professor Peter Doherty says he thinks it more likely the flu season is spawned by more time spent close together indoors during winter, and agrees social distancing measures will play the biggest role in determining the shape of the new COVID-19 pandemic.

SARS was beaten back after nine months – just as summer arrived in the northern hemisphere. But experts say it was fast containment, including exhaustive case detection and isolation, that put an end to it, not the weather.

In another “rapid expert consultation” sent to the White House on April 7, a prestigious panel at the US National Academies of Science, Medicine and Engineering warned this new virus was unlikely to wane as the sun came out. More research was needed, they said. What early studies had been done were patchy, usually performed under lab conditions. While there are early signs the virus might break down faster in the heat, evidence is also emerging that it can spread further in the air and last on surfaces longer than other comparable viruses, which will factor into how it spreads.

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What's more, the other two deadly coronaviruses, SARS and MERS, “have not demonstrated any evidence of seasonality following their emergence” and even the rare influenza strains that have morphed into pandemics (such as the 1918 Spanish flu and, more recently, the less severe 2009 swine flu) did not follow the typical pattern. All had a peak second wave about six months after their emergence, regardless of the season.

“Given that countries currently in summer climates, such as Australia and Iran, are experiencing rapid [COVID-19] spread, a decrease in cases with increases in humidity and temperature elsewhere should not be assumed,” the report said. And if temperature does turn out to be a factor, the authors note it will likely be less pronounced than in the existing viruses in circulation such as the cold and flu where there is at least partial herd immunity in the population already.

How long does the virus last in the air?

The virus behind the pandemic is tiny -110 nanometres wide to be precise - but it behaves differently to the other two deadly coronaviruses to emerge in humans, SARS and MERS. Up until now, most of the evidence came from doctor's charts - the disease it causes, COVID-19, is less deadly than either previous outbreak but it can spread between people a lot easier. In less than five months, it's infected more than 2 million worldwide. New early research out of four major labs in the US has found the virus is also "remarkably" resilient in the air, staying infectious for more than 12 hours.

It is still unclear how much of the virus you would need to inhale to get sick. But researchers from America's National Institute of Allergy and Infectious Diseases and elsewhere found, unlike SARS and MERS, particles of the new virus could still infect cells in a dish and looked intact under the microscope after 16 hours.

"That's very unusual, we'd expect them to be ripped apart in the air by then," says infectious disease aerobiologist Professor Chad Roy, who co-wrote the paper. "We scientists don't use this kind of bold language lightly so health authorities need to take note."

The work has not yet been put through rigorous peer review, released on April 18 in a preprint as scientists around the world fast-track their normal "protracted" process in the face of a fast-moving and dangerous new virus. But Professor Roy says the team are confident in the findings as they had been replicated across four different labs, including the US army's virology hub Fort Detrick.

"We're all running under a fire drill, there's still so much we don't know about this virus and it's all so urgent," he says. "Of course we need more research, but in science when you see a warning light blinking on like this, you need to pay attention."

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But is it airborne?

While scientists agree the virus is not airborne in the same way as other infectious diseases such as measles, they are split on the question of how big a risk it poses in the air. The World Health Organisation says there’s not enough evidence to say the virus can jump from person to person in small or aerosolised particles. It’s mostly shed by larger water droplets from the nose and mouth, tiny balls of mucus, salt and virus that can shoot out up to about a metre when an infected person coughs or sneezes. Sometimes they land on and contaminate surfaces, but they’re too heavy to survive long in the air.

But the WHO raised eyebrows back in March when it emphatically "fact-checked" the idea that coronavirus might be airborne as "incorrect" over Twitter.

For doctors (and the general public) the term airborne calls to mind measles, or the film Outbreak, where a pathogen primarily spreads by lingering in the air. Experts agree that's not how COVID-19 is moving through the community. If it were, some experts such as infectious disease physician Associate Professor Sanjaya Senanayake say the shape of the pandemic would likely look different – moving faster and striking down more people without close contact to known cases.

But while large particles tend to carry more virus than smaller aerosols, Professor Roy says it's been assumed by health authorities such as the WHO that only big droplets will carry any live virus at all. His work in the US now adds to a growing body of evidence COVID-19 virus was also an airborne pathogen, he says.

Still that doesn't mean you'll catch it just from passing someone on the street. Like cigarette smoke, the virus will disperse in open spaces. And, just like smoke, it can build up in enclosed areas without ventilation.

"I don't know all the data the WHO have and this is not the only piece of the puzzle, but it's an important one," Professor Roy says. "I think as COVID-19 continues we will see its infection or [reproduction number] go up. It's certainly spreading easier than SARS."

A growing number of scientists, including infectious disease expert Professor Raina MacIntyre and aerosol scientist and WHO adviser Professor Lidia Morawska, agree the risk from aerosols has been underestimated. Warning signs are piling up, Professor Morawska says - the virus rips through a cruise ship even after passengers are isolated in their cabins, a choir meets in Washington and 45 out of the 60 singers leave the two hour rehearsal infected even though none have symptoms.

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As an Australian Department of Health spokeswoman also noted, viruses do not always fall neatly into either aerosol or droplet (which are classed as anything more than five microns in size). They can leave the body as both.

“It’s old medical dogma from the 1930s that they only travel a metre,” Professor Morawska said. “But we know more now. We've already shown other viruses like the flu [that mostly] shed in droplets can also spread from breathing. [In a] pandemic, we need to assume the worst. We don’t know how much you would have to inhale to get infected, the smaller particles at least carry less virus, but it’s possible."

Professor Morawska, who heads up the International Laboratory for Air Quality and Health at Queensland University of Technology, is now working with scientists from around the world to write enhanced guidelines for potential aerosol transmission.

On April 21, the Department of Health said COVID-19 was "not as efficient" at spreading in the air as other diseases considered to be airborne – a greater risk was posed by the "underestimated" spread of COVID-19 through touching contaminated surfaces. Of the new research, the government said such lab experiments were useful but at present physical distancing and hand hygiene had suppressed the spread of COVID-19 in Australia.

On paper, early studies into the new virus show mixed results – some found it in the air of hospitals treating patients, some didn’t. All viruses start to break up once they leave the body and different conditions will speed that up - usually the warmer the better. One laboratory study by scientists from the US Centers for Disease Control and Prevention detected the virus in the air for up to three hours but found the new virus did not last any longer than the original SARS strain. The WHO has since pointed out that such studies do not reflect real-world conditions.

One study tracked a cluster of infections at a restaurant in China back to one asymptomatic patient - those who had caught the virus were found to be sitting in the direct flow of air pushed by the air conditioner, suggesting, according to the researchers, that droplets were the main route of transmission.

Still, America’s National Academies of Sciences, Engineering and Medicine wrote to the White House earlier in April saying the current research supports the possibility that COVID-19 can be spread by aerosols from breathing, as was observed to a small degree during SARS. But back then in 2003, Associate Professor Senanayake notes the virus generally aerosolised in hospitals where treatments such as intubation and ventilation increase the risk. The WHO itself has issued warnings to healthcare workers that this may happen again and many wards treating COVID-19 operate as if the infection is airborne, including in Australia. "We're all following that really closely and it seems to be holding up well," Associate Professor Senanyake said.

Face masks: recommended in the US but not in Australia.

Face masks: recommended in the US but not in Australia.Credit: The Age

Should we be wearing face masks?

Face masks can protect against the droplets that spread the virus and are now a common sight on the streets of many cities around the world such as Hong Kong. Both the WHO and the Australian government say masks are still only necessary for people with symptoms and those treating them, and must not be wasted by the general public as shortages of the product could put healthcare workers at risk. All the same, calls are growing in many Western countries for a wider take-up of face masks to slow outbreaks.

In the US, the CDC has already reversed its own advice, given research showing even people without symptoms can spread the virus. It now urges people to wear cloth masks whenever they are somewhere poorly ventilated or can’t keep their distance from others, such as a supermarket aisle. Its guidance to healthcare workers also states that, while the extent of aerosol transmission is still unclear, the virus can spread when someone "coughs, sneezes or talks". Aerosol scientist Professor Lidia Morawska agrees with the move, saying masks aren't needed outdoors but are a good idea where ventilation is poor. But infectious disease experts Professor Raina MacIntyre and Associate Professor Sanjaya Senanayake say they are not as necessary in Australia as in places such as New York, where community transmission is now rampant. Experts all agree good protective gear is crucial for healthcare workers - Professor Roy says the new US research underscores the need for high quality masks that protect against aerosols as well as droplets.

It’s also unclear how much home-made masks, or bandanas and scarves, will block virus-laden droplets. Some experts warn widespread use of DIY masks could leave people with a false sense of security - and an urge to touch (and so possibly contaminate) their face more often as they adjust them. Australian health authorities have indicated they are reviewing their own advice on masks, as they do all their guidelines, but stress it still stands.

Chief Medical Officer Brendan Murphy has urged people not to "waste" masks and notes they should be handled carefully and changed regularly (Nobel prizewinner and medical researcher Peter Doherty recommends sterilising used masks rather than throwing them away, given the shortage).

Is air-conditioning and heating safe?

Right now, health authorities say anyone who spends more than two hours in an enclosed room with an infected person has been exposed to the virus. But Professor Morawska warns there needs to be more focus on the need to opt for natural ventilation by throwing windows open wherever possible rather than using air circulation systems.

Associate Professor Senanayake says air-conditioning and heating could still be considered safe in most settings as droplets will not travel that far. And the Department of Health agreed that, while there was not enough data on the question, the risk from ventilation was low outside healthcare settings.

NSW Health said it considered air-conditioners and heating safe to use even when people in the home had COVID-19. "What is important for suspected and confirmed cases is to try and stay in a room separate to the rest of their family and, if possible, use a different bathroom ... to avoid the spread of COVID-19 through droplets ... and surface contamination," a spokeswoman said. "It is only in the very sickest patients, who are in our specialist ICUs, or patients who require hospital treatments like intubation, where we are likely to see the virus be airborne."

Scientists say the virus is genetically linked to bats but new research suggests it might have first jumped into the endangered (and heavily trafficked) pangolin (above) before crossing into humans.

Scientists say the virus is genetically linked to bats but new research suggests it might have first jumped into the endangered (and heavily trafficked) pangolin (above) before crossing into humans.Credit: Getty

What does wildlife have to do with the new coronavirus?

Scientists think the virus jumped from wild animals into humans, likely in late 2019 somewhere in a bustling wet market in Wuhan, central China, where many of the first cases of COVID-19 emerged. Such wet markets are notorious breeding grounds for disease as stressed animals from all corners of the world are caged close together, trading unfamiliar diseases, and then handled and butchered by humans. It happened that way with SARS, the first deadly coronavirus outbreak, and then again with the second, MERS, this time along camel trade routes and slaughterhouses in the Middle East. As people push farther into the world's last wild places, more viruses previously unknown to humanity are making the leap across species lines.

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But in April when China lifted lockdowns on Wuhan, it also reopened wet markets, sparking concern it hadn't learned the lesson of either SARS or COVID-19. Australia's Prime Minister Scott Morrison has slammed the move as unfathomable given what is known about the market's risks to human health (Chief Medical Officer Professor Brendan Murphy echoed his concerns, saying "zoonotic [animal] viruses are our biggest risk and clearly that risk is much greater when you have animals close together".) The World Health Organisation has also warned against wet markets but has so far refused to condemn China for the move. WHO special envoy and UN representative Dr David Nabarro noted that the organisation cannot police countries, it can only advise them and its advice is to shut the markets down.

Breaking the wildlife trade's hold on China will not be easy - while young generations are moving away from wild meat, it has a long history in culture and traditional medicine. Add to this the staggering amount of money China has tied up in the trade as the world's biggest producer and consumer of wildlife products. Scientists have long been warning that habitat loss, global travel and a persistent appetite for wild animals has created a “perfect storm” for the next human pandemic. But the trade continues to boom, worth billions through both legal and illegal channels in South-East Asia, Europe, the US and beyond. Demand is growing alongside middle-class wealth in much of the developing world.

China is now under fire for its refusal to outlaw the sale of many wild species after SARS – from the critically endangered tiger to animals linked to that earlier outbreak such as civets and bats. In February, as COVID-19 cases continued to explode within its borders, China announced seismic laws to outlaw the sale of all wildlife for food and restrict their commerce for medicine, pets or research. But by April, the government was also offering tax breaks to ship wildlife products overseas (a perk not extended to medical supplies) and even advising the public that unproven traditional remedies including bear bile could help patients critically ill with COVID-19. Beijing had initially blamed the wildlife trade for the outbreak, but its Foreign Ministry spokesman Lijian Zhao has since ignored research showing the natural origins of the virus in favour of unfounded conspiracy theories that it did not emerge in China at all.

Why is there talk of testing sewage for the virus?

One of the main reasons this coronavirus is so dangerous is because it can spread well before symptoms show up. That makes the virus fairly infectious, and it also means government responses are often one to two weeks behind. Currently, the best way of tracking coronavirus is testing people with symptoms – but what if we were able to find out where the virus was before the sore throats and high fevers hit? Australian experts have begun tests on Canberra sewage to see if they can pick up traces of coronavirus in our faeces. It's not glamorous, but it could be lifesaving.

A study out of the Netherlands appears to suggest that the first coronavirus traces emerge in sewage matter roughly a week before symptoms appear in humans. If Australia sees the same results, the government could get a headstart on the virus, better allocating health resources to outbreak areas, or even tightening and loosening social distancing measures based on whether the virus is present in your local sewage.

To do the testing, Australian National University epidemiologists will piggyback off the daily sewage tests already required for wastewater management. Scientists will centrifuge samples (spin them to separate fluids from solids) then test for the virus. It's not yet known whether a rough number of coronavirus cases can be determined from examining the sewage – they’re looking into that, too. – Max Koslowski

What's Zoom and what's it for?

Video calling is having a moment, thanks to tight social distancing rules across the globe, and Zoom is now the service of choice for everything from family catch-ups to hosting virtual parties.

Zoom offers free video conference calls, up to 40 minutes in duration and capable of connecting as many as a 100 people, with the service almost entirely catering to a business audience prior to the coronavirus pandemic.

The app is easy to use, with no logins required, and has a number of other bells and whistles thrown in that’s made it a hit. There’s the Touch Up My Appearance beauty filter to make users look their best during calls and the virtual backgrounds feature that lets you choose any image – a tropical island, a lavish palace interior – as your background.

But these same features make Zoom a risky service as well. The biggest problem is that of uninvited guests taking advantage of the lax security settings on Zoom to intrude on virtual meetings. With consumers sending links (meeting IDs) of Zoom meetings across various social media platforms, that information is being used by online trolls to sign in and disrupt proceedings. The other big issue has been Zoom’s usual practice of letting people jump into a meeting without providing the necessary credentials, again letting trolls listen in on a conversation.

Zoom, by its own admission, was unprepared for the spike in demand and has moved to plug some of the security holes. But it’s a work in progress and a number of organisations, from Google and NASA to schools across the US and Singapore, have already banned the use of the service. With social distancing rules to remain in place for some time, Zoom’s unlikely to see a dip in usage and for those keen to press ahead with their virtual cocktail parties and book clubs on the app, here’s our guide to using the services safely. 

– Supratim Adhikari 

Can you catch COVID-19 from pets?

It appears that, as with SARS, it's possible for our pets to catch the virus from us in very rare cases. But despite hysteria about an asymptomatic Pomeranian in Hong Kong returning a "weak positive" test for COVID-19 (and a tiger also catching a mild dose, from a keeper, at the Bronx Zoo in New York), the World Health Organisation stresses there's no evidence the virus can jump the other way, from pets to people, and no one should abandon their animals.

Hong Kong authorities tested 17 dogs and eight cats from households with confirmed COVID-19 cases or people in close contact with confirmed patients and found two dogs that tested positive – the Pomeranian and a German Shepherd – but they did not appear to show symptoms. They concluded that pet dogs and cats couldn't pass the virus to human beings, although they could test positive if exposed by their owners.

If it were possible to catch coronavirus from your pet, two veterinary experts looking into the US tiger case told The New York Times, it would have already become a clear factor in this pandemic, given the huge numbers of cases, and other scientists have since echoed the sentiment: there hasn’t been a single case. While the virus is thought to have jumped from wild animals into humans and mutated, that was one “spillover” event, likely at a wet market where wildlife were caged and killed in close contact with people, and there is no evidence of another species jump.

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One small study that did cause a stir online found that cats and ferrets could be infected and pass on the virus to one another (dogs and farm animals were less susceptible) but it’s important to note the context for the research – animals in the study were deliberately infected with very high doses of the virus to see if a possible vaccine could be tested on them. And researchers did not find they could then give the virus to humans.

“We’re not overly concerned about people contracting COVID-19 through contact with dogs and cats,” the American Veterinary Medical Association's chief veterinary officer Gail Golab has told The Washington Post, adding “the virus survives best on smooth surfaces, such as countertops and doorknobs. Porous materials, such as pet fur, tend to absorb and trap pathogens, making it harder to contract them through touch.”

“The current spread of coronavirus in humans is the result of human-to-human transmission,” said Australian Veterinary Association President Dr Julia Crawford on March 11. “To date, there is no evidence that pets can spread the disease, or that they can become sick.”

The WHO is now investigating the case of the tiger – which showed mild symptoms but is said to be recovering well – as well as a possible infection in a cat in Belgium and the two dogs in Hong Kong to understand how pets may get the virus. It’s “important we remain respectful and kind” to any animals co-infected with humans, says Dr Mike Ryan, executive director of the WHO’s health emergencies program. “They’re victims like the rest of us.”

In Australia, the federal government says there have been no cases detected in any domestic animals here (pets or livestock) or wildlife, and the current virus is spreading between people not animals.

Testing for the virus in animals requires different testing kits and, while Australia “does have capabilities” to do it, it's not a priority given “the latest scientific information”. The US Centers for Disease Control and Prevention also does not consider there to be evidence of a threat from animals. It instead advises you to “protect pets” if you yourself are sick, limiting contact, but otherwise you should exercise the usual precautions around animals.

With pets now revelling in their owners being home with them under strict new social distancing measures, follow commonsense hygiene. “What owners can do is what we always recommend," says Dr Crawford. "Please practise good hygiene, including washing your hands before and after handling your pets, as well as their food.” You can still take your pets to the vet and walk them but don't attempt to disinfect your cat, it could hurt them.

Why do virus death rates vary so much worldwide?

Anyone following the international news on the pandemic will have noticed a marked variation in death rates from COVID-19 among different countries. In hard-hit Italy, for instance, the death rate among confirmed cases is around 12 per cent in the first week of April, compared with 1.75 per cent in Germany and – thus far – less than 1 per cent here. East Asian countries have generally done better, the UK, Spain and the US worse.

A number of factors help account for this variation. The most significant is that the death rate will largely reflect how widely you are testing, and the age groups you test in. If, as in Germany, you test a very large number of people, many of whom are young with mild symptoms, you get a lower rate of death overall. If, as in the UK and US, you only test those who are very ill and in hospital, the converse applies: your death rate looks much higher. Per head of population, Australia’s testing regime has been ahead of many other countries.

Other factors that contribute to varying death rates include: demographics such as the age profile of a country’s population overall; density of living conditions; patterns of interaction between different generations; cultural factors (such as the absence of social kissing and handshaking in Japan); and, importantly, the capacity of health systems to cope with the very ill. Germany has more than double Italy’s number of acute care beds per 100,000 people, and more than triple the UK’s acute bed capacity.

In Italy, with one of the oldest populations in Europe, researchers believe that deeply ingrained habits of adult children living with, or remaining housed close to, their parents has contributed to the high fatality rate there. Younger adults, commuting into larger employment centres where the virus had been silently spreading, bring the virus back to the smaller communities where their parents live. Smoking rates may be a factor in some places. The jury is out on whether seasonality (whether a country is going into warmer or cooler weather) plays a role. – Deborah Snow

Why do we have social distancing and rules on not doing things?

The virus needs us to move; it jumps person to person after close contact so the idea is to slow its infection rate by temporarily changing our behaviour through physical distancing As the world waits for a vaccine, this will save lives by helping stop a surge of cases overwhelming emergency departments all at once. Along with measures such as lockdowns and tracing and isolating cases, social distancing has worked against outbreaks in the past, including the Spanish Flu of 1918. The recent surge in Australian cases has started to slow a little in recent days as new rules come into force. But if people do not follow them, Chief Medical Officer Brendan Murphy warns that Australia could lose its window to contain the outbreak – and cases could rapidly explode. In some countries, including Australia, the virus's reproduction number – or the likely number of people each person will infect – has already fallen from its natural average of two to three. If it keeps falling, to below one, the virus will start to die out on its own. Deputy Chief Medical Officer Professor Paul Kelly says Australia is on the cusp of killing off the virus but the government has flagged pursuing full elimination of the virus (along the lines of the tough lockdowns seen in New Zealand) would be too costly.

When can I leave COVID-19 isolation once I get better?

The federal government has stopped tracking recovery numbers in Australia, drawing criticism from some experts who say it is an important measure of any outbreak. Amid a shortage of testing kits, an Australian government spokesman confirmed only healthcare and aged care workers returning to the frontline must be "cleared" with testing (two negative tests) under the national guidelines. Local health authorities keep a close eye on all confirmed cases on the virus and others may still be retested. But most, such as those recovering in home isolation, only have to meet the following conditions:

  • 10 days have passed since falling ill
  • AND symptoms have been gone for 72 hours

The US Centre for Disease Control and Prevention advises the same 72-hour window of time after symptoms disappear but some studies overseas have shown the virus can live in the body for weeks after.

The Australian government spokesman said "a small proportion of people may have an illness that has completely resolved but their [tests] remain persistently positive". There a decision on release from isolation will be made on a case-by-case basis after consulting their doctor, the testing lab and the public health unit.

The 72-hour rule was decided by the Communicable Diseases Network Australia, which advises Health Minister Greg Hunt, as "a precautionary period to manage uncertainty around how long a confirmed case remains infectious post-symptom resolution", the spokesman said.

"Even in these patients there is uncertainty around whether there is a direct correlation of persistent [positive tests] and infectivity, but what we know from other virus infection, it is not a neat correlation," he said. "There have been case reports of patients testing positive for a couple of weeks post-symptom resolution, but are viral culture negative meaning they are unlikely infectious for very long after symptoms resolve."

How should I handle takeaway coffee?

Wash your hands after holding your cup. "It's all about interrupting the chance of self-inoculation," says Associate Professor Ian Mackay, an expert on coronaviruses, at the University of Queensland. The virus has been found to last for shorter periods on card and paper than some other surfaces but it can persist, according to lab studies. "Whether there is ever likely to be enough virus on that surface to infect another person remains an unanswered question," says Professor Mackay.

"The overarching rule here is simple: wash your hands before you touch your face if you have come into contact with something that is likely to have been contaminated with virus." 

What's the death rate from COVID-19?

Calculating the mortality rate of a pandemic that is still spreading is an imprecise science – people may be diagnosed or succumb to the illness further down the line. Based on the first 55,000-odd cases recorded in China, the WHO estimates the fatality rate so far as 3.4 per cent. But, given so many milder cases will go under the radar, most experts, including the WHO, agree the true number is likely closer to 1 per cent.

That makes it more than ten times deadlier than the flu but less dangerous than the other two rare coronaviruses to emerge in humans: SARS-CoV, which also caused global panic when it exploded onto the scene in late 2002, and MERS-CoV, which causes a condition more deadly again known as MERS (Middle East Respiratory Syndrome). On the raw figures so far, more than five million people have been infected worldwide and at least 328,000 have died. About 1.8 million have already "officially" recovered. The case of the Diamond Princess outbreak has offered one of the most stable data sets yet from which to make calculations- analysis of deaths and infections there put the overall fatality rate at just below 1 per cent.

Am I going to die?

Data out of China found most people (about 80 per cent) recovered from the new virus on their own, even if they developed pneumonia. But about one in five needed more serious medical intervention (such as ventilation to help them breathe) and, of those, 6 per cent were pushed into critical care – as multiple organs began to fail along with the lungs, or septic shock (whole-body infection) set in.

Anyone can catch the virus – but people most at risk of complications are older or have other conditions such as diabetes or heart disease, making their bodies may be less able to cope with the extra strain. Smokers are also more likely to develop a nasty infection, as the virus breeds via cell receptors in the lungs known to increase with cigarette smoke. Experts say the higher the dose of virus you are hit with, the faster you will show symptoms and the more dangerous it can be for your immune system to fight off. For example, catching the virus from a doorknob is likely to give you a smaller dose than caring for an infected person without protective clothing such as a mask. For more on how the new virus affects the body and what it feels like to get it, you can read this explainer here.

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What treatment is given in intensive care?

Difficulty breathing is the main reason that people with COVID-19 present to a hospital, says the head of the Alfred Hospital’s intensive care unit, Associate Professor Steve Mcgloughin. The virus, which attacks the lungs, can progress quite quickly, worsening beyond shortness of breath. Once admitted to a ward and receiving oxygen via a mask, a person’s condition may improve – but other people will need increasing amounts of support to keep their lungs sending oxygen throughout their body.

"That’s where intensive care would step in,” says Dr Mcgloughin. “If it’s bad enough that you need to be put on a breathing machine then you would definitely be in intensive care. If there was a sense that a patient was deteriorating towards needing a ventilator or a life-support machine, we’d also put them in intensive care. What intensive care is able to offer is the medical specialists and more monitoring … It's very intense – not surprisingly, given the name.”

Without a drug that is definitively proven to halt or even slow COVID-19 at this stage, the aim is to support patients until they recover. “We wait for the virus to clear up and then the lungs will often repair themselves if we can wait and just support them while they do that. So you might have a period of, say, a week on a life-support machine where the virus starts to clear itself and the lungs start to improve and then we take the breathing machine away.”

But, as experience has shown worldwide, the outcome is not always positive. “Keeping people in a sort of induced sleep, the energy demands of their body go right down,” says Dr Mcgloughin. “They’re not using as much oxygen as they would normally. The problem with that is it works quite well and it’s a really effective therapy but, obviously, being in that state puts the body in quite a vulnerable position.”

There are two problems that can arise, he says. One is that the infection itself can affect the other organs. And there is “just the stress of being so sick”. “We're supposed to be up and walking around but when you’re in intensive care your body is a little bit vulnerable to either getting another infection from bacteria, or the virus itself affecting your other organs. That’s why there is a difference, unfortunately, that people who are a little bit older or those a bit more vulnerable beforehand don’t do as well as people that are younger.”

Dr Mcgloughin, who chaired the group that wrote the COVID-19 guidelines for The Australian and New Zealand Intensive Care Society, says Australian hospitals are benefiting from the advice of colleagues overseas, including in Italy and Singapore, both about treatments and how to protect themselves. “Within weeks of what happened in Italy, they had already published very detailed summaries of what happened. I’m amazed the guys were able to do that.”

So what would he say to younger people, including those aged 20-29 who have been diagnosed with COVID-19 in NSW and Victoria more than any other age group?

“Stay home. Do what the government’s asking us to do. Let’s do that for a week or a few months. You’re doing it potentially to protect yourself – it’s not impossible that young people get sick – but you’re really doing it to protect the older people in our community. To me, it’s a real social responsibility. It’s sort of a good test of Australians' ability to look after each other, really. You know, we all like to think we do that – but this is probably the chance to prove it.”

How are ventilators used to treat COVID-19?

Anyone who’s had a general anaesthetic will have relied on a ventilator, whether they know it or not. It happens between the bit where you start to feel drowsy – ”you stop breathing and then I put in a breathing tube and put you on to a breathing machine,” says Dr Suzi Nou, president of the Australian Society of Anaesthetists – and the bit where you wake up in the recovery room. That breathing machine is a ventilator, pushing oxygen into your body. “For healthy patients undergoing routine surgery, [when] I stop giving them anaesthetic, they start breathing for themselves,” says Dr Nou.

Treating patients with COVID-19, whose lungs are compromised by the disease, is another story. “They’re too unwell to do the job of breathing for themselves. We’d induce the state of sleepiness, put a breathing tube in and put them on the ventilator.” While a patient having routine surgery will rely on a ventilator for minutes or hours – and it’s not uncommon for a patient in intensive care to rely on one for four or five days – a patient with COVID-19 might need one for as long as 10 days.

This is why ventilators have become such a precious commodity worldwide since the pandemic took hold, prompting a doctor in the hard-hit Italian region of Lombardy to say they had become as precious as gold. There are plans for the number of ventilators (and intensive care beds to go with them) in Australia to be doubled to 4000 while more have been freed up by the suspension of non-urgent elective surgery and still more are now being manufactured in Australia.  

But behind every ventilator is a team of experts too, such as Dr Nou and highly trained nurses. In Australia, every patient on a ventilator has a dedicated nurse. It's these professionals who need to be supported to keep coming to work in the coming weeks and months, says the head of the Alfred Hospital’s intensive care unit, Associate Professor Steve Mcgloughin. "Everyone is very focused on the machines," he says, "but the most valuable resource we have in healthcare is the people."

How long does it take to recover?

Symptoms tend to clear up in just a week or two in mild cases or three to six for more serious, according to WHO data. But early evidence suggests the virus can stick around in the body even longer in some cases. Australian researchers have now mapped the body's immune response, identifying the antibodies it recruits to defeat the new virus, in some people starting the fight within just three days of the initial infection. Experts say it’s too early to say if this illness will result in permanent damage, such as the lung tissue scarring seen in more severe SARS and MERS patients, but some are worried it might as more evidence of the virus's impact on organs such as the heart and lungs emerges.

I'm over 70. Should I self-isolate?

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The federal government is urging those aged 70 or over (as well as those with a chronic condition over the age of 60 or Indigenous people over 50) to stay home "where practicable", avoiding contact with others as much as they can, including family such as grandchildren. If you fall into these categories, this measure is designed to protect you, not keep you a prisoner at home. You can still go outside or shop if necessary but it is best to opt for delivery or seek help from family, friends or even the local council to get supplies. Visits to aged-care homes have also been restricted to protect vulnerable elderly residents.

Deputy Chief Medical Officer Paul Kelly says Australians weighing up whether to bring elderly relatives home to care for them now face a difficult "trade-off". On the one hand, Professor Kelly says "the most frail, elderly people requiring, for example, a lot of home care ... may be best to shelter with relatives". But if other family members are going "out into the world ... and interacting with others", they risk bringing the virus into the home. The answer isn't always clear-cut and will come down to personal circumstances.

But I’m young and not at high risk. Why can't I socialise?

While the elderly and those with underlying conditions are more likely to die from COVID-19, young people can too. Figures from China, Europe and the US show concerningly high hospitalisation rates among the under 60s and in Australia there are people under 50 already in need of intensive care. There have been more coronavirus cases among 25- to 29 year-old Australians than any other age group. In any case, even if you're young and get a milder case you can still spread the virus to someone who might not be so lucky.

How long does the virus live on surfaces?

Viruses need hosts to survive – they can't make it on their own. So far, the best evidence we have on how long the virus lasts on surfaces comes from a letter to the editor by a team of American scientists published in The New England Journal of Medicine, one of the world’s top medical journals. The data is still early stage and needs to be interpreted with caution. They placed samples of SARS-CoV-2 on plastic, stainless steel, cardboard and copper and tracked what happened to the virus. The virus was the most stable on plastic and stainless steel and could be detected up to 72 hours later. On absorbent surfaces such as cardboard, fabric or paper it degrades much faster. However, the amount of the virus fell quickly over time. On plastic, for example, it halved in about seven hours. That indicates these surfaces do not remain infectious forever.

The overarching rule here is simple: wash your hands before you touch your face if you have come into contact with something that is likely to have been contaminated with virus.

Professor Ian Mackay, coronavirus expert

Copper has broad anti-microbial properties and has been installed in some hospitals around the world to stop the spread of antibiotic-resistant superbugs. When a bacterium or virus lands on copper, electrically charged particles known as ions jump from the surface into the bacterium, punching holes in it and killing it. Some scientists have suggested that copper doorplates and doorknobs be installed in healthcare facilities and public places in Australia.

It is possible, although unlikely, exchanging cash could transmit the virus. Using a card is “probably lower risk”, write Professor Ian Mackay and Dr Katherine Arden on The Conversation, because you keep the card and don’t have to touch other people. In fact, using "tap and pay" is a social distancing practice recommended by the federal government. - with Liam Mannix

What about takeaway food?

You can still order in food but authorities say you shouldn't let the courier into your home and, if in an apartment, you should pick up the order outside rather than inviting them through a security door into a communal area.

Professor Peter Doherty says that while food delivery is unlikely to be a major source of infection, it's something to keep in mind when you're "taking hold of the pizza box".

"Before you take the food out, wash your hands and then put the pizza box somewhere out of the way," Doherty suggests in a webinar for the Australian Academy of Science. “It can certainly survive longer on plastics and steel ... in the SARS epidemic, of course, we saw people wiping down elevator buttons. […] Just open everything, wash your hands before you take the food out of the plastic and maybe transfer it to another plastic bag before you put it in the fridge."

Should I disinfect my fruit and vegetables?

No. The Centre for Food Safety’s guidelines say there is no evidence the virus that causes COVID-19 can be passed on via food. The US Centres for Disease Control and Prevention agrees. Food should be washed with water before you eat it. Soap or dishwashing liquid should not be used, as they can stay on food and cause sickness. There is no need to wash food you are going to cook, as the heat will kill the virus, says Arden. You also don’t need to scrub food that you are going to later peel, such as oranges.

Touching produce and then touching your face is more relevant. “Think of your hands as the enemy,” write Professor Ian Mackay and virologist Katherine Arden. If the virus comes into contact with your hands, and then you touch your nose, mouth or eyes, it can gain entry to your body. You must wash your hands with soap and water thoroughly before eating. - Liam Mannix

What temperature should I do my laundry?

We don’t need to be worried about the temperature of a wash because we use strong detergents in our washing powders, even when they are cold wash formulations, says virologist Katherine Ardern and coronavirus expert Associate Professor Ian Mackay, both at the University of Queensland. They cite a recent study, which, although not having yet been through a peer review process so not conclusive, provides an early picture of how the virus reacts in certain conditions. In a laboratory, a 30-minute incubation of the virus at 56C or a five-minute incubation at 70C rendered SARS-CoV-2 inactive. In its recommendations for households where someone is ill, or suspected of being ill with COVID-19, the US Centers for Disease Control and Prevention recommends laundering items "using the warmest appropriate water setting for the items", and drying the items completely.

Will my dishwasher kill the virus?

A similar answer applies as with washing machines. Coronavirus expert Professor Ian Mackay notes that if you are caring for an ill person, you need to be extra vigilant in cleaning their crockery and cutlery to ensure that you limit the risk of family spread. The US Centers for Disease Control and Prevention says this if someone has COVID-19 in your household: "The ill person should eat/be fed in their room if possible. Non-disposable food service items used should be handled with gloves and washed with hot water or in a dishwasher. Clean hands after handling used food service items."

What disinfectant should I use on surfaces?

The NSW Health Department advises using common household disinfectant sprays for surfaces. SARS-CoV-2 is what is known as an “enveloped virus”, which means it is made of a little ball of fat and protein. That makes it relatively easily to kill with standard disinfectants.

In Australia, disinfectants are regulated by the Therapeutic Goods Administration, so if you pick the right one – look for a specific disinfectant, not a cleaner – you can be confident it works. Not all disinfectants are regulated by the same standards. Look for a specific label on the disinfectant that means it kills viruses, such as virucidal or antiviral activity. Importantly, this is different to antibacterial – antibacterial ingredients kill bacteria, not viruses.

Make sure you follow the instructions on the label, which may include cleaning a surface before disinfecting it. Cleaning and disinfecting are different things. As the CDC notes, cleaning does not kill germs in itself but, by removing them, it lowers their numbers and the risk of spreading infection. The Australian Department of Health advises you to target frequently touched surfaces: door handles, bed rails, table tops and light switches.

As with all things COVID-19, there is still much we don’t know. The advice above is based on guidelines from the US Centers for Disease Control and Prevention, guidance from the Australian Department of Health, from the Australian Research Council Training Centre for Food Safety, and expert commentary from Associate Professor Ian Mackay (an expert on coronaviruses) and Katherine Ardern (a virologist), both at the University of Queensland. – Liam Mannix

How does COVID-19 compare to the flu?

"Let's stop saying it's a bad flu," pleaded doctor Daniele Macchini, from the northern Italian city of Bergamo, where the virus had gained a deadly foothold. Patients inundating intensive care wards had "far from the complications of a flu", the doctor wrote on Facebook in March.

While flu has many of the same symptoms and results in tens of thousands of deaths worldwide every year, COVID-19 is more than 10 times deadlier. In Australia, government figures for the most recent flu season ending October 2019 show 812 people died of influenza out of 298,120 reported cases – a fatality rate of about 0.27 per cent.

Emerging coronaviruses such as this strain and SARS can also do more damage to the body, particularly the lungs. And the new virus is more infectious than the flu, or SARS or MERS, with one COVID-19 patient likely to infect between two and three others.

Can you get COVID-19 and the flu at the same time?

Yes, it's possible. As it breeds in the lungs, the virus can impair your body's ability to filter out germs falling down from the upper airways and so leave some people susceptible to another bug – whether the common cold, influenza or a case of bacterial pneumonia. So this year there is a particular urgency behind calls for people to have their flu shots. On April 1, Deputy Chief Medical Officer Paul Kelly urged Australians, especially those aged over 65, to get their flu vaccines as soon as possible. "As of now there are millions of vaccines out there ready," he said.

How long will the pandemic last?

That's the big question. This virus's closest relative, SARS, while deadly, spread more slowly and to far fewer countries and so early containment efforts worked to wipe it out, largely within a year. For COVID-19, many experts are instead drawing parallels with the 1918 Spanish Flu pandemic, which killed millions around the world because it spread so far. The good news is medicine has taken a quantum leap forward since then. Still, modelling by the Imperial College London suggests countries will need to use control measures such as social distancing, aggressive case detection, even shutdowns right through until a vaccine becomes available – between 12 and 18 months.

What are other countries doing to 'flatten the curve'?

Some nations, including many in Europe, have turned to the "China model" of forced home quarantines and transport shutdowns to stop the virus. But experts note that China, as well as countries such as Singapore, Taiwan and South Korea, have also started to "flatten their curve" of infection growth through exhaustive testing, contact tracing of known cases and community take-up of "social distancing" measures such as working from home or taking schools online.

China's success so far means it is already starting to relax many of its lockdowns, even as it braces for a potential second wave. In Italy and now other countries such as Spain, France and the UK, people are only allowed to leave their homes to run essential errands such as grabbing groceries (and they must queue 1.5 metres apart).

    What's the difference between JobSeeker and JobKeeper?

    JobSeeker is a payment of $550 a fortnight (now increased to $1100 a fortnight as part of a coronavirus stimulus boost) for those who have lost their employment. JobSeeker replaced the NewStart allowance in March. However, the new JobKeeper scheme is a $1500 payment (before tax) per staff member provided to employers by the government over the next six months to help businesses hold onto workers so that after the pandemic is over they can more easily start over. Employers can only receive the subsidy if they have turnover of less than $1 billion and this figure has fallen by 30 per cent or more, or they have a turnover higher than $1 billion and this has fallen by 50 per cent or more. Employers receiving the subsidy must report to the Australian Tax Office every month. See here for details. – Jennifer Duke

    I have asthma. Am I more at risk?

    At least one in 10 Australians have asthma but the condition doesn’t mean you’re more likely to catch COVID-19. The problem is that because your lungs are already inflamed, it can leave you open to a more severe case or trigger an asthma attack. “It’s a double-whammy, really,” says National Asthma Council Australia chief Siobhan Brophy.

    Respiratory physician Peter Wark says there’s not enough data yet to know exactly how COVID-19 affects asthmatics but, from previous experience with other respiratory illnesses, they’ll likely be at higher risk of complications – as was observed during the SARS outbreak and still occurs with common illnesses such as cold and flu. The WHO and other health authorities are urging extra precautions for asthmatics. Brophy says now is the time to be on your “best behaviour”: following your asthma plan and doctor’s advice to the letter and re-filling prescriptions so your lungs are in their best shape possible should an infection come. While people without the condition have been hoarding ventolin, she notes there’s little point as the medication is designed to treat an asthma attack and not COVID-19.

    There has been some concern about continuing asthma medication such as steroid tablets or injections, which could suppress the body's overall immune system, Brophy says, but steroid inhalers are still fine – they only travel to the lungs and remain vital for asthmatics. “Talk to your doctor before you stop taking anything but if you’re still using an old nebuliser to take your medication, use a puffer and a spacer instead. A nebuliser will spray out particles [and possibly germs] from your lungs." Tell your doctor about your asthma and your medication if you develop symptoms.

    Don't coronaviruses only cause colds?

    Coronaviruses are a family of viruses causing respiratory illness mostly found in animals. Only seven have been identified in humans, including the four that commonly give us coughs and colds. But when a new strain jumps across from wildlife, such as SARS and now this new strain, it can be dangerous as there is no natural immunity to fight it off.

    Why are there so many names for the virus?

    Because it's new, at first the virus was known simply as the "novel" coronavirus. Then the WHO named it SARS-CoV-2, given it shares so much of its DNA – about 75 per cent – with the SARS-CoV strain behind the SARS outbreak. The illness caused by this current strain is COVID-19.

    Where did the virus come from?

    The illness was first identified after people started falling ill at wet market reported to sell wild animals in the Chinese city of Wuhan. Unfounded theories that the virus is man-made quickly began to circulate online but scientists studying its genome already agree it came from animals - as more than 70 per cent of all new diseases emerging in humans do. Wild animals packed together and then butchered in live markets throughout Asia can be incubators for viruses to evolve and jump species barriers – SARS was traced back to a colony of bats but was believed to have passed into humans again in a wet market via the Himalayan palm civet, an ancient species of mammal eaten as a delicacy in China. And MERS also has bat origins but mostly spreads from infected camels, often in slaughterhouses. Bats are essential to many ecosystems we rely on but, through a lucky quirk in their immune system, they also carry a whole host of diseases that do not harm them. Early work suggests this new virus is 96 per cent similar to a SARS-like strain already discovered in bats a few years back, but experts think it likely first jumped into another animal, possibly the highly endangered and heavily trafficked pangolin, where it gained potency before passing into humans.

    How does self-isolation work?

    The question of who should practice this social distancing (everyone) versus who should seal themselves off completely has sparked some confusion. To stem the spread of COVID-19, millions of people infected or exposed around the world are also being urged to go into voluntary exile at home or in isolation wards. While some people have chosen to start home isolation themselves, thousands of others in Australia been already been issued formal notices to comply as states call in police to help enforce them.

    We dive into the rules in this explainer here but in brief: if you have been in close contact with a confirmed case of COVID-19 or have returned from overseas, then you must self-isolate for a full fortnight (the estimated period of virus incubation before symptoms appear). If you are self-isolating at home, your household can still go out but you should try to keep to yourself, wearing a mask around others, ordering in food rather than going out, disinfecting common areas and keeping a close eye on how you are feeling (symptoms to watch out for are a high fever and shortness of breath). If you are infected yourself or awaiting tests, then everyone should stay home.

    You can still wander into your garden or balcony but, while some officials have said you can walk the dog or stretch your legs, Deputy Chief Medical Officer Paul Kelly says you must stay home if you've been told to self-isolate: "Sorry."

    Despite these rules, Chief Medical Officer Brendan Murphy said, on March 27, that Australia was still seeing large numbers of returned travellers with the virus and, in many cases, passing it on to their families. “More than two-thirds are returned travellers, and a significant proportion of the other cases have been transmitted from returned travellers,” he said. From March 29, all overseas arrivals are being escorted from airports into hotels and other accommodation for the 14-day window, at the government's expense. The army has been called in alongside police to enforce these quarantines after a number of people were caught out of their homes breaking isolation orders.

    Can I still travel?

    Only if you really have to. Our borders have closed and overseas travel is now banned under biosecurity powers, except in exceptional circumstances. Citizens still travelling abroad are urged to come home as countries impose similar shutdowns of their own.

    Starting with Tasmania, most states have closed their domestic borders - police patrols will now ask people crossing over to go into quarantine for the recommended 14-day window.

    How does the virus affect pregnant women – and babies?

    At this early stage, we are still not absolutely sure how the virus affects women and babies. Different governments have offered different advice.
    For now, let’s stick to what Australia’s peak body, the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZOG), has to say. Note these guidelines are changing regularly and you should check back on their website for the most up-to-date advice. According to guidelines, at this stage it does not appear that pregnant women are at greater risk from COVID-19 than the rest of the population – as they were during the world's last pandemic Swine Flu in 2009.

    However, they tend to be more susceptible to respiratory illnesses in general, such as the flu. There is no evidence of an increased risk of miscarriage or birth abnormalities, nor is there evidence the virus can pass from woman to unborn child or via breastmilk. “The safest place to birth your baby is in a hospital, where you have access to highly trained staff and emergency facilities,” the guidelines state. If the mother is infected at the time of birth, she should not be separated from her newborn, but should wear a mask and take precautions. The health advice is the same for pregnant women as it is for everyone else: work from home, avoid public places, and nail your hand hygiene.

    Are pregnant women allowed to have a support person in the labour ward with them?

    The RANZCOG guidelines suggest visitors in hospital are limited only to the immediate partner. But this is just a suggestion – different hospitals will have different rules.

    Is public transport stopping?

    No. Public transport is still running as it is considered one of the essential activities exempt from the government's ban on gatherings but cleaning has been ramped up. While calls are growing from some experts to shut down public transport already, many people rely on it. Still, as social distancing rules come into force, travellers are deserting normally packed routes in droves. When on public transport, health officials say you should allow room for others as much as possible, rather than crowding in. It's also important to keep an eye on what you've been touching. If you then touch your face, a virus surviving on, say, a metal handrail could jump across – so carry a disinfectant or even wear one (stylish) glove for holding on and touching things.

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    How far away is a vaccine?

    The most hopeful estimates fall within the range of 12 to 18 months. A report for the British government put it at “potentially 18 months or more”. Why? Because making a vaccine is really, really hard. To make a vaccine, you first need to design a way of giving a human immunity against a virus. Then you need to make sure the vaccine is not toxic. Then you need to test it in animals. Then you need to test it in humans – and the tests need to be large so we can make sure it works and is safe. And then you need to make the billions of doses needed. And there is every chance a vaccine that looks promising in the lab, or in animal tests, won’t work in humans. Experts are hoping to roll out a safe vaccine within 18 months. But even that would be unprecedented. No vaccine has ever been developed that quickly. - Liam Mannix

    What treatment is being developed?

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    The Peter Doherty Institute in Australia is working on both a vaccine and a potential therapeutic treatment for the virus, and director Sharon Lewin says the latter might offer a faster fix. A drug that could block the virus from replicating in the body (or calm down the body's intense immune response to it) could keep patients with severe infections alive and, in the case of an antiviral, reduce transmission. Several existing drugs are now being trialled against the new virus worldwide, including those used to treat HIV, malaria, and arthritis. The results look promising but it's not time to rush out to the pharmacy just yet. Read more about treatments being explored, including a tablet to prevent the virus in the first place, here.

    How does this outbreak compare to others such as SARS?

    It took this new coronavirus 48 days to infect the first thousand people. By contrast, SARS took 130 days and the less infectious MERS more than two years to infect a thousand people after it emerged in 2012. When SARS finished its spread after nine months in 2003, only 8098 cases had been confirmed across 26 countries but close to 10 per cent of those were fatal. (Most clusters happened in hospitals or households.) MERS has been circulating for eight years across 27 countries so far, and kills about a third of those who fall ill – out of about 2500 confirmed cases. Ebola is even more deadly, killing more than 40 per cent of those diagnosed over a number of outbreaks since the 1970s but it has been reported in just a handful of countries.

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    In the pandemic records, the infamous 1918 Spanish flu killed about 2.5 per cent of its victims over two years – but because it infected so many people (close to 27 per cent of the world's population) at a time of much cruder medical care, about 50 million died. Today, doctors are much better able to stave off secondary bacterial infections, which proved particularly deadly during that outbreak. And, unlike the Spanish flu, young people are not dying at the same high rates.

    The last pandemic was swine flu in 2009, the second coming of a H1N1 influenza that infected between 11 and 21 per cent of the world's population. Governments mounted costly responses until it was ruled to be over in October 2010. But the virus killed about 285,000 people (fewer than seasonal flu normally does) with a relatively low fatality rate of .02 per cent, and the WHO copped criticism for labelling it a pandemic at all.

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    What happens if I lose income?

    Billions of dollars are being poured into the Australian economy to offset the damage being done to businesses and employment by the coronavirus pandemic. For details of who gets what from stimulus packages, look here.

    Centrelink payments have been lifted and expanded. And, in a bid to stop companies cutting jobs, employees of eligible businesses can claim a new $1500 fortnightly 'Jobkeeper' payment, even some who have already been let go so long as they were with the company on March 1. Businesses and not-for-profits that have experienced more than a 30 per cent downturn in revenue are eligible and payments will be delivered in May but backdated to March.

    The federal government estimates about half of the workforce - or six million people - will get this payment over the next six months.

    If you've lost your job because of the crisis, this explainer outlines what support is available.

    Our team will answer more questions and update information in this story regularly.

    If you suspect you or a family member has coronavirus you should call (not visit) your GP or ring the national Coronavirus Health Information Hotline on 1800 020 080.

    Let us explain

    If you'd like some expert background on an issue or a news event, drop us a line at explainers@smh.com.au or explainers@theage.com.au. Read more explainers here.

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