Australia is on the cusp of curbing COVID-19. But there's one number to watch: growth factor.

Australia’s Deputy Chief Medical Officer, Professor Paul Kelly, says we’re on the “cusp” of seeing the coronavirus die out locally.

Despite the fact that new cases continue to be reported daily, there are positive signs that Australia is succeeding in flattening the curve.

So what is the best indication of how Australia is tracking?

It’s called the growth rate. Also known as the growth factor, R0, infection rate or the reproduction number.

Watch: Mamamia breaks down your most common questions about COVID-19. Post continues after video. 

Here’s exactly what it means, how to calculate it, and what it is in Australia.

What does the growth rate mean?

Essentially, the growth rate measures how contagious a disease is by telling us the average number of further infections one case will cause.

For example, if the growth rate number was 5, it would mean that, on average, one infected person would be the cause of a further five infections.

As epidemiologist expert Professor Joseph Eisenberg writes for The Conversation: “If R0 is less than 1, the disease will die out in a population, because on average an infectious person will transmit to fewer than one other susceptible person. On the other hand, if R0 is greater than 1, the disease will spread…

“When public health agencies are figuring out how to deal with an outbreak, they are trying to bring R0 down to less than 1.”

It’s specifically used for new diseases that are infecting vulnerable populations where no vaccine is available.

So how is it calculated? It’s simple. You take the number of new confirmed cases and divide it by the previous day’s new cases.

What is the COVID-19 growth rate in Australia?

Prof. Kelly says the reproductive rate has been somewhere between one and two in Australia, meaning every infected person infects between one and two others.

“Where you want to be is below one, so less than one other person being infected after a person themselves has the infection,” Prof. Kelly told reporters in Canberra on Friday.

“Once you get to that point the virus dies out or the epidemic dies out.

“At the moment we’re probably on the cusp of that in Australia… whether that’s where we’re going to be in several weeks or months remains to be seen.”

In recent days, the growth rate has indeed dropped below one — a very positive sign.

But as Prof. Kelly stressed “we’re not at that stage yet”, warning Australians that they need to remain vigilant in the fight to flatten the curve of case numbers.

How does social distancing help the growth rate?

Without the social distancing measures currently in place, one positive person could lead to 400 other cases within a month, Prof. Kelly said on Friday.

"That is the sort of explosive epidemic we've seen in other countries. We just cannot afford, at this stage, to be considering that happening."

Asked if allowing international flights into Australia would be the last restriction to be lifted down the track, Prof. Kelly noted: "We are an island, of course, and that's our advantage."

As of the morning of Saturday, April 11, there are 6,262 confirmed cases of COVID-19 in Australia. There are 86 new cases since the 24 hours prior. The nation-wide death toll is 55.

Read more: 

• 'Can I go to my holiday house?' What you can and can't do this Easter long weekend.
• 'Can I have COVID-19 without knowing?' What you need to know about asymptomatic cases.
• What causes a 'second wave' of disease outbreak, and could we see this in Australia?

- With AAP. 

To protect yourself and the community from COVID-19, remain in your home unless strictly necessary, keep at least 1.5 metres away from other people, regularly wash your hands and avoid touching your face.

If you are sick and believe you have symptoms of COVID-19, call your GP ahead of time to book an appointment. Or call the national Coronavirus Health Information Line for advice on 1800 020 080. If you are experiencing a medical emergency, call 000.

To keep up to date with the latest information, please visit the Department of Health website.

Feature Image: Getty.

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