Reproduction number key to reducing Victoria's COVID caseload

Burnet Institute

07 August, 2020

With metropolitan Melbourne now in Stage 4 lockdown, Burnet Institute Deputy Director, Professor Margaret Hellard AM, has urged the community to cooperate with restrictions to drive down the state’s daily case numbers.

Professor Hellard told The Age that the enhanced restrictions may be the thing that drives the COVID-19 reproduction ratio – the R number – below one.

She explained the importance of the R number, and said that if it drops below one, Victoria’s daily case numbers will start to decrease.

“If we are to get that R value to get down and stay down, we need community co-operation, this is not just about a government bringing in a restriction measure it is about the community engaging in the response,” Professor Hellard told The Age.

Analysis from Burnet, published by the Medical Journal of Australia earlier this week, found that the R number fell from 1.75 at the start of July, to 1.16 at the end of the month, because of Victoria’s Stage 3 restrictions.

8,314 cases of local transmission were diagnosed in Victoria in July. Without the Stage 3 restrictions, the researchers estimate there would have been 27,000 cases, and potentially up to 45,000 in July.

Victoria COVID-19 Cases Averted July

Professor Hellard explained that an R ratio of 1.75 means 10 people with COVID-19 would infect 17 or 18 others. The current ratio means 10 people will infect 11 or 12 others.

“For this week it is not surprising that we will have the same number of cases, if not 10 per cent more cases, because of the R value being what it is,” Professor Hellard said.

“Hopefully in a week or two weeks the R value will fall below one and we will see a decline in the number of cases each day after that.”

Professor Hellard said that a vaccine is likely to take a long time, meaning the solution to COVID-19 is in the hands of the community.

“In the next 18 months, we’re not going to get a vaccine or silver bullet cure for coronavirus. The solution to how we manage this has to come from within the community.”

You can read the full story on The Age website.

Optimise COVID-19

Professor Hellard is one of the Chief Investigators on Burnet’s Optimise Study, which uses strategic information and mathematical models to make predictions, and to inform national policy.

Find out more about Professor Hellard’s work, and the Optimise study.

Contact Details

For more information in relation to this news article, please contact:

Professor Margaret Hellard AM

Deputy Director, Programs; Adjunct Professor, Monash University, DEPM.




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