Coronavirus: Australia’s fatality rate one of lowest, but that’s not whole story

Australia’s low COVID-19 fatality rate reflects high testing rates and the fact our hospitals have not been overwhelmed, experts say.

Australia has one of the lowest case fatality rates in the world for COVID-19. Picture: istock

Australia has one of the lowest case fatality rates in the world for COVID-19, with experts saying that reflects high testing rates and the fact our hospitals have not been overwhelmed.

The case fatality rate is the ratio between confirmed deaths and confirmed cases of COVID-19 and does not necessarily reflect the true mortality rate.

Case fatality rates vary widely around the world. Britain has one of the highest CFRs in the world, at 15.44 per cent. Italy’s CFR is 15 per cent and the US stands at 4 per cent. Australia’s CFR is 1.19 per cent, according to data from Johns Hopkins University.

Having a higher CFR does not mean that the virus is more deadly in that country, said Paul Glasziou, a professor of evidence-based medicine at Bond University. “The major difference around the world is probably the case detection rate,” Professor Glasziou said.

“So if you miss a lot of people who did have COVID but didn’t need to go to hospital that are undetected by testing, you’ve only got the sickest people in your statistics­ and you get an apparently higher death rate per case.’’

Fatality rates can also rise when healthcare systems are overwhelmed, as the sickest patients cannot get access to ventilators and are more likely to die.

“And the age structure of the population and who gets infected is also a third factor,” Professor Glasziou said.

Australia’s low case fatality rate reflects the fact that testing is widespread and most cases in the community are therefore being detected. In addition, our hospitals have not been overwhelmed.

Death rates in the US have lowered in recent weeks, despite an increase in the numbers of detected cases. Greater levels of testing and a shift in the age demographics of those being infected by the virus have been postulated as reasons for the downward trend.

Professor Glasziou said he expected­ the death rates to once again climb in coming weeks.

“The southern states in particular, like Florida and Texas, have been getting their real first waves, so the cases have been rising,” he said.

“So if you simply divide the number of deaths by the number of cases, it looks much better at the moment, but that’s because they’re in the early phase.

“This is a transition between states like New York, which have been coming back down — they’ve had most of the people who were going to die have died.

“So that death rate from those early waves in the US is settling down and we’re now seeing the new cases coming from the southern states coming back up again, so I don’t think that case fatality rate is going to stay stable.”

A much better predictor of the true mortality rate of COVID-19 is known as the infection fatality rate. It captures the rate of deaths among confirmed cases, as well as those with undetected disease who are asymptomatic or haven’t been tested.

Last week, the World Health Organisation put forward its most recent estimate of the infection fatality rate of COVID-19.

The agency’s chief scientist, Soumya Swaminathan, said the current consensus among scientists for now was that the IFR is about 0.6 per cent. However, older people are at much higher risk of dying from the disease.