Experts say they know how to stop coronavirus — it's all about whether Australia can take the right steps.

See how coronavirus is spreading around the world — and what lessons we can take from the countries beating the virus.

Just two weeks ago coronavirus was an issue at the edges of the Australian consciousness. Now the globe is in crisis and the country is shell-shocked.

Globally, the COVID-19 pandemic has now reached more than 2.8 million known cases, spread to 185 countries, and caused more than 200,000 deaths.

The data in this story was last updated on April 25 2020.

Just like in this chart, there's a lot going on, and it's very hard to understand what it all means. Well, we're here to help.

By pulling this chart apart and then helping you put it back together, this story aims to help you understand:

how quickly coronavirus is spreading in different countries;

where Australia fits into the global picture;

what we can learn from countries that appear to have curbed the rise of COVID-19; and

what you can do to help keep Australians safe.

But first, one concept that's vitally important to understanding a pandemic is exponential growth. This is a pattern viruses tend to initially follow, due to the way they're spread.

The result is that what might seem like a small difference in the rate of growth can actually have enormous impacts on how many people are infected overall.

One good way to think about the exponential spread of coronavirus is to look at how long it takes for the number of cases in a country to double.

Let's look at three different scenarios — one in which the number of cases doubles every two days, one where cases double every three days, and one where cases double once every week.

Initially, the differences might look small.

But as time passes the differences increase dramatically.

By week three, the differences are stark — and remember this example started from just one case. Not to mention, the coronavirus pandemic is predicted to run for months.

It's for this reason that early intervention can have a huge impact. One single infection in the early days of the outbreak can easily scale into hundreds, perhaps even thousands over time.

The flipside, of course, is that every infection avoided early in the outbreak can have a huge positive impact.

What does that look like in the real world? Let's look first at the source of the outbreak, China.

As you can see, in China the virus initially spread exponentially, with the number of known cases repeatedly doubling in less than two days during the early part of the outbreak.

But it now appears the country has reduced that growth, slowing new cases to a virtual trickle.

Now coronavirus is spreading much more quickly in other parts of the globe.

However, because outbreaks in each country started at different points in time, it's difficult to compare exactly how, say, Australia's growth rate compares to China's in the early days of its outbreak.

So, let's do two things to help make this a bit easier to understand.

Firstly, let's narrow it down to a few key countries so we can make it a little easier to read.

And now, let's change it so that we start tracking cases day-by-day from the moment when each country hit 100 cases. Instead of using the exact date, this brings each country onto roughly the same timeline.

But it's still difficult to compare the early days of each outbreak, because they're all so compressed down near the bottom of the chart. To aid with this, we're going to change the vertical axis of the chart to a logarithmic scale.

This means that instead of rising in a linear fashion (1, 2, 3 etc), it is scaled by powers of 10 (10, 100, 1,000 etc). This is a particularly useful way to view coronavirus cases because the virus itself spreads exponentially rather than in a linear fashion.

It's a little hard to wrap your head around, unless you're a maths whiz. But here's another way to think about it. If a country's cases are growing exponentially, it'll appear on this chart as a straight line headed up and to the right.

And the angle of the line indicates just how fast it's growing.

These guidelines show the pace of growth the same way the dots at the beginning of the story did.

You can see that for most countries, like Italy and China, the line goes up steeply early on. Their case numbers grew very quickly.

In Singapore and Japan though, the line is flatter. The case numbers grew much more slowly. That's another view of the "flattening the curve" goal everyone has been talking about.

Now that we can clearly compare countries, let's zoom into the especially important time when the virus first takes off.

We've achieved this by cutting off the vertical axis at 50,000 cases. (So keep in mind that the lines for China, the US and Italy all extend off the top of this view of the chart.)

What we want to see as much as possible are lower trend lines for each country — more like Singapore and the latter part of South Korea's trajectory, and less like Italy.

If the rate that people are being infected is slower, that means fewer people are seriously ill at the same time, and that puts less pressure on hospitals, allowing them to better care for the people who really need it.

In the case of COVID-19, older people are most at risk and typically require the most care. But if healthcare systems are overwhelmed, as in Italy, doctors may need to prioritise who they are even able to treat.

As you can see, Australia is still in the earlier stages of its outbreak. It hit 100 cases 51 days after China and 16 days after Italy.

But after an initial spread, which saw the cases doubling close to every three days, Australia appears to be beginning to control the virus.

What's worked to flatten the curve?

We're now going to take you through the responses of the following countries — Singapore, South Korea, Italy, the United States and China. And then we're going to explain what measures Australia has implemented, and how we're tracking compared to those countries.

(If you want to skip straight to Australia, well, we wouldn't really recommend it but, okay, you can.)

Singapore

Let's start with the measures implemented in Singapore, a country of 5.8 million people, which was touted as an early success, but has since been dealing with a second outbreak.

Singapore reported its first case of coronavirus on January 24, just one day before Australia's first case. However, like many Asian countries, it had learned important lessons from past epidemics — in Singapore's case that was the SARS outbreak in 2002 and 2003.

Within three days of its first case, it had implemented thermal scanning of all people arriving at Changi International Airport. A strict quarantine on anyone who had been in Hubei followed, and on February 1, it barred all visitors who had been in China within the past 14 days.

On February 17, when there were 75 confirmed cases of coronavirus, the government issued a 'stay-at-home' notice to everyone who had been in China in the previous two weeks.

To date, Singapore has not closed schools, though school holidays started on March 14.

Dale Fisher, the chair of infection control at Singapore's National University Hospital, writes in The Conversation that the key to its response was how well it executed the strategies of quarantining and tracing people who had come into contact with the virus.

"A couple times a day, you'll get an SMS and you have to click on a link that will show where your phone is," Mr Fisher explains. "In case you cheat and leave your phone at home with someone else, the government has people knocking on doors now and then. The penalties are pretty harsh."

On February 26, two people were charged under the new Infectious Disease Act of giving false information and obstructing contact tracing.

However the country also shows how quickly an outbreak can spread despite early success.

Just as other countries were looking to Singapore for answers, cases begun to grow in the country's migrant labour community.

As of April 14, out of 3,252 cases recorded in Singapore, 1,625 were linked to outbreaks in migrant dormitories.

The Government has now ordered the rest of the country to stay home and maintain at least a one-metre distance from others if going out for essential needs like food shopping, and the number of new cases reported in the wider community has inched downwards.

While this outbreak shows how quickly the situation can change, the early work Singapore did on controlling the virus means it does this from a stronger position that most other countries around the world.

These measures may work in a city-state like Singapore, but will they work in a bigger country, and can you use them to control COVID-19 once it gets into the community?

One country that has managed to do exactly that, drastically reducing new cases after an initial spike, is South Korea. Its response, too, could hold some salient lessons for Australia.

South Korea

Like Singapore and another success story, Taiwan, South Korea's response was informed by shortcomings in fighting a previous disease, in this case MERS, which claimed 36 lives in 2015.

Even before the country had any confirmed cases, quarantine and screening measures were in place for arrivals from Wuhan as of January 3.

The first case was reported on January 20.

By February 20, the case numbers had leapt to 104. Two days later, the government raised the threat level, empowering it to shut down religious gatherings, restrict movement and access South Koreans' personal data. It also shut daycare centres, banned outdoor rallies and postponed the re-opening of schools in early March.

Professor Allen Cheng, an infectious diseases specialist at Monash University tweeted: "South Korea has had a model response despite early setbacks."

Lots of testing was a critical part of that model response. South Korea created a network of 96 public labs and began testing nearly 20,000 people a day, including at drive-through testing stations. South Korea has tested more people than most other countries — more than 280,000 tests as of March 19. (That's one in every 180 people.)

That testing regime may account for the steep initial rise in cases. But combined with aggressive contact tracing, it also means the country has been able to actively chase down cases of infection.

While it initially had among the highest confirmed COVID-19 cases in the world, these measures appear to be working. The death toll from the virus is less than 200, and the rate of growth has also slowed to a trickle.

This indicates that the measures South Korea has implemented can work to significantly change the trajectory of the spread even once coronavirus establishes a major presence in the population.

With countries in Asia appearing to be doing a better job in slowing the spread of the virus, the epicentre of the outbreak shifted to Europe.

Italy

In the early stages of the outbreak, Italy and South Korea were on a similar trajectory, however the impact on each country has been drastically different.

So why has Italy's health system been so overwhelmed, and why have so many more people died in Italy?

Italy reported its first coronavirus cases on January 31, two weeks after the first case in South Korea. The government immediately suspended flights from China, Hong Kong, Macau and Taiwan and declared a state of emergency.

Then on February 21, the first coronavirus-related death was reported and Italy announced a cluster of 15 cases in the Lombardy region, which would become known as the 'Italian Wuhan'. By March 1, the number of cases there had exploded to 1,128.

It is too early to be certain of why cases spread uncontrolled in Italy. A number of reasons have been touted. One is that the virus was circulating unnoticed, possibly from the middle of January, because many infected people had no symptoms or only mild symptoms.

An Italian health researcher noted that there was an unusually high number of pneumonia cases in January. Unlike in Taiwan, they weren't tested for coronavirus.

But from the start the country's social distance messaging was muddled, with regional politicians downplaying the need for it and many Italians ignoring the advice anyway. Unlike in South Korea, there were no recent memories of a pandemic to draw on.

Hassan Vally, associate professor of public health at La Trobe University, says Italy was slow to react.

"As soon as you have uncontrolled spread that is occurring before you're doing anything to limit the spread, you get this exponential growth in cases," he says. "They were late to the party."

Also, research shows that the virus is disproportionately affecting older populations. The death rate among Italians with coronavirus aged 80 and above has been around 20 per cent, and 12 per cent for those aged 70-79. Those two groups account for nearly 90 per cent of Italy's deaths.

While Italy is being used as the warning for what Australia could face, there are still positives to be learnt from the country.

The town of Vo at the centre of the outbreak leapt into action after its first COVID-19 death, testing the entire town, which showed 3 per cent of people were infected despite most not showing symptoms. After two weeks of strict quarantine, the researchers carried out another round of mass testing in Vo. The rate of COVID-19 infection had dropped from nearly 3 per cent to 0.41 per cent.

United States

If our Asian neighbours are examples of what we should be aiming for, in the coming weeks the United States may offer another insight into what happens if the COVID-19 response is handled poorly.

The US began screening travellers from Wuhan on January 17, and the first case was reported on January 23. It stopped visitors who had been in China from entering the US on January 31 and US citizens who had been in China had to self-quarantine for 14 days.

By mid-February, case numbers were up to 15, but by that stage, only 54 tests had been done by public health or Centres for Disease Control (CDC) laboratories.

The US bungled the rollout of COVID-19 testing through a combination of flawed tests and bureaucratic red tape between federal and state agencies. By March 4, it had passed its 100th case but had still only performed just over 1,000 tests, at a time when the Korean Government was testing 20,000 people per day.

While the government was issuing public health notices about large gatherings, hand washing and other advice, no action was taken to enforce any social distancing.

President Donald Trump, after initially downplaying the threat of the virus, abruptly changed tack, and a massive effort is underway to increase the amount of testing.

But the response is still plagued with mismanagement, including shortages of test kit equipment and chemicals, and even crowdsourcing requests for gear from local officials.

Some areas, including New York City and Seattle, have acknowledged their failure to contain the virus and have abandoned efforts to test lots of residents, and simply told them to stay at home instead.

The United States is currently tracking at the highest rate of infection at a time when countries like South Korea and China have slashed the number of new infections, and has eclipsed China as the country with the highest number of infections.

China

As Donald Trump talks about winding back restrictions by Easter, worryingly the US doesn't look to be implementing the measures China used to control COVID-19 after it exploded in Hubei province.

After mismanaging the initial outbreak in Hubei, China enacted a lockdown across much of the country, and turned the mechanism of its surveillance state to trace the movements of everyone who may have been infected and enforce the strict lockdowns.

In particular, the practice of quarantining patients with minor symptoms away from their homes helped drastically reduce the spread of the virus in the community.

Currently, almost all cases being recorded in China are from returning travellers, and while questions remain about whether China can now restart its shuttered economy without a second wave of infections, it is the largest example of how to rein in COVID-19.

So what can Australia take from this?

Around the world there are three strategies that seem to be working — acting early, extensive testing and contact tracing, and physical distancing — and according to Hassan Vally they are the same ways people have been effectively combating the spread of disease for centuries.

"If we want to control a pandemic or an epidemic, we need to identify cases early, we need to isolate cases, we need to stop people coming into contact with each other," he says.

"So these are all the simplest public health measures available, but also the most effective.

"All of the countries that are doing well are utilising those methods, they're obviously implementing the methods in slightly different ways, but I think it's a combination of all of those methods together and being implemented in a very rigorous way that is leading to great outcomes for many places."

While Australia's trajectory initially sat above countries like Singapore, there is evidence that some early decisions the Government made, like restricting arrivals from China, helped to delay the spread of the virus en masse.

The Government has drastically ramped up measures to halt the spread of the virus — closing down borders, asking returning travellers to self-isolate, shutting down businesses, and telling people to "stay at home unless it is absolutely necessary to go out".

What about testing and contact tracing?

To date, Australia has done more than 200,000 tests for coronavirus. Prime Minister Scott Morrison says we have some of the highest test rates in the world, and the lowest rate of positive tests.

Professor Vally says if we are to bring the virus under control we need to be testing as many people as possible.

"The answer to this epidemic in Australia is social distancing and the rapid contact tracing and isolation of cases. Mass testing of contacts is going to be important so that we identify all cases, including those with mild and no symptoms, who may be spreading illness."

Compared to those countries who have so far controlled the spread of COVID-19, our contact tracing and quarantine enforcement is far less stringent.

Returning international passengers are being trusted to self-isolate without checks, and the release of infected passengers from the Princess Ruby cruise ship highlighted weaknesses in the system.

However, there is change afoot. On Tuesday night, the Prime Minister announced the Government was looking to Singapore for solutions to better enforce quarantines, and today announced that all returning international travellers would be quarantined for two weeks in a hotel upon arrival. Police around the country have also begun checking in on people who are self-isolating at home to make sure they are not leaving the house.

The challenge lies with all of us

Now the virus is being spread in the community, by far the most important measure for individual Australians is to drastically reduce the contact they have with other people.

With governments attempting to retain some activity in the economy, it's tempting to think this can just be solved by more restrictions, but Professor Vally says this isn't the case.

"We're now at a point where the biggest influence on how this is going to play out are individuals," he says.

"So it's not the Government, and it's not some magical technological advance or cure.

"It's how well people will listen to the advice to practise social-distancing measures, because that is going to be the greatest influence on how much this virus is transmitted."

Professor Vally says until a vaccine or treatment is found there isn't going to be a solution that will allow us to relax.

"We have to get comfortable with a great deal of uncertainty and that's not something that we like. As human beings, we don't like uncertainty.

"People haven't seen a threat to their health like this before, even with SARS and a few other things, in everyone's mind they're a big story and then a few weeks later we're back to watching the football results or politics or whatever, and that's been the pattern for most people's lives. Well, this is different."

By exploiting the interconnectedness of the world we live in, COVID-19 removes the luxury of thinking we are in control of our own lives. We are at once uniquely vulnerable to the actions of other people, and responsible for their safety.

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