Why Sydney’s two-week lockdown extension won’t be enough to stop Covid

Sydney won’t be able to open up even once the two-week lockdown extension is complete, an expert says, pointing to one key figure.

The two week extension of Greater Sydney’s lockdown won’t be enough to bring down Covid-19 cases to a point where authorities can open up, one expert says.

University of South Australia epidemiologist Professor Adrian Esterman said two weeks would not be sufficient.

“Not at all,” he told news.com.au. “If you think about it, it’s taken four weeks to get to where we are now. Even if they are flattening the curve now it will take at least another four weeks to get down to single digits again.”

Prof Esterman said even if the state was not aiming to get cases down to zero – NSW Premier Gladys Berejiklian has said authorities are focusing on cases infectious while in the community – authorities could not lift restrictions until cases were at least in the single digits.

“Other states also won’t open their borders unless cases are in single digits,” he said.

Prof Esterman also pointed out that the virus’s reproductive number – also known as Reff – needs to be under one in order for cases to come down and it was still at 2.4.

“This is the highest it’s been so at the moment it doesn’t look like the curve is even flattening yet,” he said.

The five-day moving average, which provides a better idea of the trend, is still going up, and is at 85 cases a day.

“What I want to see is the moving average coming down,” he said.

RELATED: Greater Sydney lockdown extended for at least two weeks

NSW's five-day moving average. Source: Adrian Esterman

The Reff (reproductive number) needs to be under 1 for the outbreak to start dying out. Source: Adrian Esterman

Prof Esterman said it was very difficult to predict how quickly cases would come down at this point but once the curve was flattened then it would be possible to get a better predictive model.

“At the moment we’re not even sure we’re at the peak yet,” he said.

Prof Esterman said epidemic curves, including the one for Melbourne’s outbreak last year, tended to be fairly symmetrical.

“If it takes four weeks to get to the peak, it probably takes four weeks to get to the base,” he said.

If the curve is flattening now in Greater Sydney, Prof Esterman believes this will be seen in the next four or five days as the changes to restrictions introduced on Friday begin to have an impact.

“But the restrictions are still slacker than those in Melbourne last year and it could be that we need further tightening before we see the curve flatten out,” he said.

“We all wish NSW the best but at the moment, unless there is some change in what they’re doing, I’m not sure we’re going to see the thing flattening out.”

RELATED: Greater Sydney lockdown could continue until August

Premier Gladys Berejiklian during Wednesday’s press conference where she announced a two-week extension to Greater Sydney’s lockdown. Picture: Lisa Maree Williams/Getty Images

NSW has been under pressure to tighten its restrictions, and in particular to better define what it means to be an essential worker, with many pointing out that shops like Ikea and Harvey Norman are still operating.

But Ms Berejiklian said most of the transmission in workplaces had been happening in places like supermarkets or health facilities that have to stay open, and through mobile workforces.

On Wednesday, there were 97 new covid cases recorded, including at least 24 cases who were infectious while in the community.

Ms Berejiklian has stressed the number of cases infectious in the community would be the figure deciding how long lockdown was necessary.

“We have said that the number of infections in the community, we want to get down to zero,” she said. “If we have cases in isolation, that is less of a concern to us.”

She told reporters lockdown would be extended for “at least” two weeks.

“We will know at the end of two weeks to what extent we need to extend the lockdown, whether there is any chance of face-to-face schooling,” she said.

“There are a number of issues we won’t know until we have further data.

“Remember the impact of some of the changes we are put in place will not be felt for the next few days.

“The reason why we want to provide that two-week period at least is so that parents who are teaching children or supervising children from home know that unfortunately for an additional two weeks at least their children will need to learn from home.”

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