The federal government is “not in a position” to give projections about how many Australians may be infected or die from the coronavirus, the health minister Greg Hunt said, with 128 infections including three deaths confirmed.
“We are not at this stage in a position to put out particular figures because the modelling has been evolving all of the time,” Hunt told reporters on Tuesday in a press conference with the deputy chief medical officer Prof Paul Kelly.
Kelly added: “We are getting the best modellers in Australia who are linked with the international community to look at a variety of scenarios, but as minister Hunt said, the most important thing at the moment is finding cases, finding the contacts and isolating. That is the way we slow down the epidemic and decrease the number of cases in our community.”
In recent days researchers have made a variety of predictions about how widespread the impact of the virus might be, including projections that up to 70% of Australians could become infected and 400,000 may die, or that 3,000 people might die “in a best case estimate”.
But chair of the Infection Prevention and Control Expert Advisory Group, Prof Lyn Gilbert, said: “The estimates are often so widely different you’re probably better off not believing any of them”.
“There are a group of modellers doing a lot of work informing the decisions of government, but specific figures are not being mentioned by government for good reason – because everyone recognises modelling at this stage of an epidemic has limitations,” Gilbert said.
“It’s too complicated to be putting numbers out there in the public domain without being able to explain what the data is based on, and also what assumptions are made about the policies implemented which also make a difference in terms of how long it takes local transmission to occur and when the outbreak will peak.
“Governments make decisions based on a range of possibilities and other factors that may change.”
On Thursday morning, the premier of New South Wales, Gladys Berejiklian, announced there were now 77 cases across that state, out of 128 in Australia.
Most of the cases are patients who have travelled overseas or who have had close contact with a confirmed case in Australia.
But NSW’s chief health officer Dr Kerry Chant said there were cases presenting in the state without an obvious epidemiological link, suggesting the Covid-19 was spreading in the community undetected.
“What is more challenging is that we have had cases where we can’t find an epidemiological link,” Chant said.
“Overnight, we have seen cases being diagnosed in people without overseas travel. Those cases are being thoroughly interviewed to ensure that we can identify any links to other confirmed cases to build up our picture.”
Infectious diseases physician Prof Peter Collignon described some of the estimates of Australian infections and deaths as “garbage”.
“We don’t have enough parameters to do any accurate modelling and I still think that’s the case,” he said. “We still don’t have an antibody test. The current test is a PCR test, which tests the virus’s genetic material and the trouble is you only really pick up people with symptoms and not milder disease. You can’t fine-tune modelling until there is more accurate data.”
Once an antibody test was developed, he said, researchers would have a better indication of the true infection and mortality rate.
“What we do know is that people who are older have a much higher chance of dying even without having all the denominators available yet,” Collignon said. “The older you are the more at risk you are. That’s quite clear. That’s not a reason to panic it’s a reason to be alert and to do the things you should do all the time.
“It’s silly to say not to worry, but that’s different to panicking and doing things that are inappropriate, like panic-buying.”
Hand-washing, getting a flu-shot (since being infected with influenza may make people more vulnerable to coronavirus), and following self-isolation and testing guidelines could significantly curb the rate of infection and deaths, he added.
Professor of epidemiology Mary-Louise McLaws said modelling could be useful but its disadvantage was it was only as good as the quality of data input.
“Data that is not included in much of the modelling is data on how people behave,” she said.
“How do people respond to a request by authorities to self-isolate? How good they are at washing their hands? If people are good at all of those measures the numbers will be contained more easily. There are so many factors to consider.”
“Hopefully Australians will pull together and act like a cohesive population because we know that will help keep numbers of infection down. I would be hesitant looking just at the best and worst case scenarios because for a novel virus it can be a very inexact science. It’s helpful for planning potential hospital beds and the response, but providing good health care is complex.”