Chinese shoppers wear masks in Beijing. The rate of new coronavirus cases continues to decline in that country.

Chinese shoppers wear masks in Beijing. The rate of new coronavirus cases continues to decline in that country.Credit:Getty Images

What about other outbreaks 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.

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.

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.

Where did COVID-19 come from?

Coronaviruses are commonly carried by animals such as bats and rodents and then passed on to humans through contact with blood,faeces and other bodily fluids. 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 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.

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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.

China has already temporarily banned its wildlife trade amid the outbreak. But,under pressure from citizens,conservation groups and experts who say the country has not learnt the lesson of SARS,this time Chinese President Xi Jinping ismoving to permanently outlaw selling wild animals for food and to further restrict their trade for medicine,scientific research and as pets.

What is shutting in Australia and how big is the risk from COVID-19 here?

The federal government has ruled people shouldn’t gather together at all except for “essential” activities such as school,public transport and work under new social distancing rules likely to last for the next six months. As well as banning outdoor gatherings of more than two people,it has closed indoor venues such as pubs,clubs,casinos,cinemas,gyms and places of worship. Auctions and open houses must stop;and play centres,libraries,community centres,galleries,institutions and more have shut their doors. Supermarkets,shopping centres and businesses such as hairdressers can stay open (under new restrictions) but restaurants and cafes will be takeout only. Indoor gatherings still running should allow space for one person per four square metres but schools will move to online learning after Easter (except for kids who have to attend in person). Weddings can have only five people present,including the couple,funerals 10 people – and house parties could be outlawed.

People shouldn't gather with more than one other person outside unless they are all from the same household and visitors to homes are now mostly banned as states call on their emergency powers to enforce the new restrictions.

Right now in Australia Prime Minister Scott Morrison says you should stay home unless you are:

Non-essential access to aged care home has also been cut back to protect elderly people. Those over 70 (as well as people with a chronic condition over 60 or Indigenous Australians aged 50 and above) are now urged to stay home and away from people outside their household,even family,as much as they can,instead leaning on delivery or help to get their shopping and supplies.

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Australia has closed its borders to foreign nationals and Australians can no longer travel overseas except in exceptional circumstances. Citizens and permanent residents will now have to see out their 14-day quarantine in hotels,at the government's expense,and those still abroad are urged to come home as other countries shutter their own borders.

Many states are now restricting domestic travel too. Tasmania has already largely closed itself off from the mainland and,in South Australia,the Northern Territory and Western Australia police will patrol borders and ask people entering to self-quarantine for 14 days.

Early cases of COVID-19 in Australia were all linked to overseas travel in China,Iran,the US or on the cruise ship turned floating quarantine site,the Diamond Princess. But more recently,a number of people including doctors and those in aged care,have been infected on Australian soil.

While extra funding has ramped up medical supplies and staff,and opened isolated"fever clinics"to test suspected cases,on the ground many doctors are still wary of a sudden surge in patients as they run low on personal protective gear like masks.

By mid-March,case numbers were doubling in Australia every three to four days but that curve has started to flatten dramatically as the new social rules take effect. Still authorities say now is not the time to"take the foot off the brake". If people do not follow the new social distancing rules,Chief Medical Officer Professor Brendan Murphy warns Australia could lose this containment window and cases could rapidly explode. Authorties have also moved to ramp up testing,amid calls from the WHO to test all suspected cases. While the criteria was strict early on because of a global shortage of testing kits,Australia has high proportionate testing rates compared to many other countries.

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We also have one of the lowest positive rates for testing in the world,Professor Murphy says,meaning authorities feel"reasonably confident that we are detecting a significant majority of cases in Australia and that means we can get on top of cases"through contact tracing. That's in contrast to countries such as Iran,Italy and even the US,where Australian authorities say they likely only tested the more severe cases or,as Murphy puts it,"when they detected significant outbreaks they probably had much,much larger outbreaks in community that were undetected".

On April 16,Professor Murphy said new modelling or"nowcasting"using current data suggested Australia was detecting more cases within its borders than anywhere else in the world. He and the Prime Minister have credited the efforts of Australia's army of contact tracers,who work around the clock to hunt down people who have been exposed to a known case of the virus.

But at times,authorities have drawn criticism for letting cases slip through the net,most notably allowing2700 passengers to disembark in Sydney from the Ruby Princess cruise ship,hundreds of whom later tested positive. But the states have also threatened hefty fines and even jail time for those at risk of spreading the virus who break home quarantine orders.

The government has ordered panic buyers to stand down as stockpiling (and even violent confrontations in toilet-paper aisles) spark fears of shortages,including for important medications such as asthma puffers. Prime Minister Scott Morrison said people can still do their shopping but if everyone floods supermarkets or disregards the new social distancing rules"more draconian measures"will be needed to slow the virus.

A 2019 report into the world's preparedness for a such a health crisis found Australia ranked highly (fourth behind the US,the UK and the Netherlands),even as researchers warned no country was fully prepared for a pandemic.

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.

This explainer was originally published on Jan 21 2020.

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