As New South Wales continues to record ever-increasing infection numbers, some epidemiologists warn the state could reach as many as 800 to 1000 daily cases within weeks.

NSW posted another record for daily COVID-19 numbers on Saturday, with 466 new locally acquired cases.

Adrian Esterman, an epidemiologist and biostatistician at the University of South Australia, said NSW daily infection numbers could soon more than double if restrictions are not tightened, starting with a tougher, Sydney-wide lockdown.

“If nothing else changes by the end of this month there’ll be 1000 cases a day,” Professor Esterman told The New Daily.

“At the moment it’s going up and it will keep going up unless something else happens,” he said.

• Related story: Restrictions tightened further in Sydney after national crisis talks

R0 rates and why they matter

The reproduction rate of the coronavirus, or R0 (pronounced ‘R nought’), is a figure that shows the average number of people a single infected individual will infect with COVID-19.

During Victoria’s second wave the R0 was a tightly held secret.

The state’s then-health minister, Jenny Mikakos, once revealed it had been as high as 2.5 on June 24 – meaning every confirmed coronavirus case would infect, on average, 2.5 people.

Chair in Epidemiology at Deakin University, Catherine Bennett, became renowned in Victoria last year for tracking the state’s R0 when the Andrews government refused to release it.

Professor Bennett was able to determine what impact restrictions had, and offered the public more transparency about where case numbers were heading.

By her calculations, Sydney currently has an R0 of 1.2, which, left unchecked, would result more than 800 cases per day in a matter of weeks.

“At the current reproduction number of 1.2 we’ll see 800-850 cases a day within four weeks,” Professor Bennett told The New Daily. 

But Professor Bennett said case numbers could fall as more people get vaccinated.

The NSW government has been heavily encouraging people to get vaccinated as a way out of the Delta outbreak, saying they need to reach six million COVID shots by the end of August to allow an easing of some restrictions.

“We expect [the R0] to start coming down a fraction, even if everything else stays the same. In two weeks we will start to see a downward pressure on the reproductive number,” Professor Bennett said.

“More vaccination and compliance will help prevent more cases and will get it to the point where the reproductive number is one.”