One question is increasingly on the minds of Sydneysiders as they watch the northern beaches coronavirus cluster grow: are we going back into lockdown?
At 144 cases, the Avalon cluster has surpassed the Thai Rock restaurant and Crossroads Hotel outbreaks in July and August.
The previous experiences and the State Government’s responses may offer hints as to the likelihood of more drastic measures, but some experts fear Sydney may have “missed the boat” already.
On July 10, the Crossroads Hotel at Casula closed after two patrons tested positive for COVID-19 and within four days, 28 cases were linked to the venue, prompting the rules around pubs and group bookings to be tightened.
The Thai Rock restaurant in Wetherill Park was the centre of a major cluster earlier in 2020. Photo: ABC News/Mridula Amin
By the end of the month 57 people had caught the virus from the Crossroads cluster, but in mid-August the numbers settled around 60.
Simultaneously, Wetherill Park’s Thai Rock restaurant was the subject of a public health alert after one staff member and two customers became confirmed cases on July 18.
It took just over a week for the cluster to grow to 70 and on August 3, it surpassed 100. But again, by mid-August, the figures stabilised — to 116.
A key difference between July’s clusters and the risk posed by the Avalon and Croydon outbreaks lies in the timing, says University of NSW epidemiologist Professor Raina MacIntyre.
“We didn’t have any predictable super-spreading events,” she said, pointing to Christmas Day and New Year’s Eve.
“New Year’s Eve is even more dangerous, and it’s predictably dangerous because of the timing.”
At exactly six days after Christmas, anyone who unknowingly caught COVID during festive gatherings would be at their most infectious.
“The fallout for New Year’s Eve could be greater than Christmas Day,” Dr MacIntyre said.
Chief Health Officer Dr Kerry Chant has acknowledged similarities in the trajectories.
“This is a little bit of a roller coaster ride,” she said yesterday, describing the volatility of risk profiles and the influence of data.
Dr Chant said “even more precautionary action” will be taken if the risk level rises due to more mystery cases where the source can’t be identified, stressing her position will change based on the numbers.
Dr MacIntyre said both the July outbreaks and the current clusters included geographic dispersal, which was an obstacle for authorities, albeit “not insurmountable”.
She said undetected transmission outside of the northern beaches could get out of hand and hoped a mask mandate would be tried before a broader lockdown.
“Generally, a lockdown is a last-resort strategy when nothing else is working,” Dr MacIntyre said.
A short, sharp, pre-Christmas lockdown would have minimised the spread around Sydney, she added.
“We’ve kind of missed the boat on the two biggest events that are going to cause a spread,” Dr MacIntyre said.
“It’s going to have to be a reactive lockdown.”
When asked whether there was a specific number of cases to trigger lockdown, Dr Chant pointed to a patient’s changing level of infectiousness.
Generally, a patient who is not hospitalised or immunosuppressed is no longer infectious after 10 days, she said, and a number of identified cases will be approaching that point, especially on the northern beaches.
“That’s why that community has borne the brunt of the tighter restrictions,” Dr Chant said.
Dr MacIntyre highlighted that any epidemic intervention worked better when applied early.
“A lockdown applied tomorrow would likely be shorter and result in a much smaller epidemic than if we waited to see how big it’s going to get,” she said.