Charts show how NSW’s current outbreak could become Australia’s worst one yet

It’s taken less than a month for New South Wales to go from the “gold standard” of COVID-19 management to an outbreak that is shaping up to be the worst Australia has yet seen. 

NSW Health reported the state’s first locally acquired cases of this wave on June 17. Three and a half weeks later, Gladys Berejiklian announced 112 new local cases amid increasingly strict lockdown measures for millions of Australians to combat the highly contagious Delta variant. That was yesterday; today there were 89 new cases.

The nature of outbreaks is that they tend to spiral out of control quickly, jumping from a handful of cases to dozens in only a day or two. 

The size of Sydney’s most recent outbreak, however, has so far exceeded Australia’s most serious outbreak at the same point as shown in graphs prepared by covid19data.com.au’s Juliette O’Brien.

Two weeks after the first case was reported, the total number of local cases in NSW’s current outbreak was higher than any other Australian outbreak so far, including Victoria’s first and second wave. 

NSW’s Avalon cluster in December 2020 started off quicker, with 101 cases after seven days compared with 31 for the current outbreak. It soon levelled out with 164 reported local cases by day 14, compared with 173 in the current outbreak.

Worryingly, the current NSW outbreak’s seven-day average for daily cases — a metric that smooths out the noise from variations in daily reporting to show the velocity of the outbreak — is ticking upwards as well. The seven-day average is lower than at the same point in Victoria’s second wave, although recent spikes in daily case numbers means this soon may change.

The current number of Sydney’s current unlinked cases are also exploding, showing that the state’s contact tracing efforts are being stretched in a way that they hadn’t in previous outbreaks.

The trajectory of outbreaks isn’t set in stone. Increasingly strict public health restrictions are meant to flatten the curve and stop the logarithmic growth in case numbers. But the current growth of NSW’s latest outbreak shows that Australia is still vulnerable and, if trends continue, could experience the worst outbreak yet.