The latest COVID-19 wave in the ACT has likely passed its peak significantly below the government's own forecasts and cases will return to lower levels in the coming weeks, experts have said.
Independent assessments of the coronavirus situation in the ACT stand in contrast to the view put forward by ACT health authorities, who had warned a fortnight ago the capital was on track to record 3000 cases a day.
However, ACT Health on Tuesday warned the wave was likely to peak in the coming weeks and the recent plateau may be a result of the school holidays reducing transmission.
Daily reported COVID-19 infections fell below 800 this week for the first time since June 14, with 712 cases reported on Sunday, July 24.
The ACT posted its highest number of COVID-19 cases on July 8, when 1701 were reported.
The number of hospitalised people with the virus reached 171 on July 18, but has followed a downward trend since.
The ACT reported 949 new COVID-19 cases on Tuesday, while 151 people who have tested positive for the virus were in hospital. Just one COVID-positive patient was in the intensive care unit and did not require ventilation.
While the number of people with COVID-19 in hospital remains high, few patients need to be treated in the intensive care unit, and a significant proportion of the overall cohort are understood to remain in hospital more than a week after testing positive for the virus.
The head of epidemiological modelling at Monash University's school of public health and preventive medicine, Associate Professor James Trauer, said the ACT's COVID wave looked to have peaked.
"It's all pointing to a decline in case rates in the coming weeks. COVID can always surprise you, but that's my current judgement," Dr Trauer said.
Dr Trauer said case numbers in the territory had been declining consistently for a couple of weeks and he could not see why case numbers would increase in the coming weeks.
Western European countries with substantial BA.5 epidemics have also reported rapid declines in their outbreaks, he said.
"NSW data suggest that most of the epidemic is now BA.5, and there don't seem to be other variants with substantial transmission advantages that would take over in the near future," Dr Trauer said.
"We've had substantial transmission over several months - so plenty of natural immunity around now. And we're also coming out of winter, with flu notifications now decreasing rapidly."
Professor Adrian Esterman, who holds the chair in biostatistics and epidemiology at the University of South Australia, said he thought the ACT had reached its peak about a week ago and was now tracking downwards.
"Without additional public health measures, numbers, however, are likely to plateau in the hundreds," Professor Esterman said.
"I think that modellers are now finding it very difficult because a) we don't have a good handle on reinfections and b) we are unsure how much of the increased transmission of BA.5 and BA.4 are due to immune escape rather than the variant being better able to latch on to human receptor cells."
Professor Esterman said the current test positivity rate for PCR COVID tests was about 20 per cent, which indicated there were a lot of undiagnosed cases in the community.
ACT Health has previously said its models assume the territory's testing regimes would miss about 40 per cent of cases in the community.
A spokesman for ACT Health on Tuesday said the most recent modelling sets completed independently by the Doherty Institute and a partnership between the Australian National University, ACT Health and Canberra Health Services both showed cases peaking about 3000 a day between mid-August and mid-September.
"It is important to note that these models try to forecast actual cases and that there will always be a level of under-reporting," the spokesman said.
The spokesman said cases had plateaued over the last fortnight.
"Whilst this may indicate that cases have peaked for this wave, it is also consistent with previous patterns of disease transmission seen in the ACT during school holidays," he said.
"The recent reduction in daily case numbers may be due to a number of factors, including improved COVID smart behaviours, under-ascertainment of cases and the impact of school holidays in reducing transmission. As such, the ACT government continues to monitor case numbers closely."
The most recent COVID and influenza epidemiological report released by ACT Health said case numbers had decreased in the week ending July 17 for the first time in five weeks "but modelling suggests we are not yet at the peak of this current COVID-19 wave".
Dr Trauer said he was not convinced ACT Health's arguments provided a strong reason to suspect case numbers would increase in the near future, but it was appropriate for health officials to be conservative in their messaging and consider factors that suggested the peak of the epidemic was still to come.
Given students have already been back at school and the downward trajectory of cases had continued, the downward trend was unlikely just to be a result of reduced transmission in the school holidays, he said.
"With Omicron, the incubation period is very short, so we should get a signal pretty soon after changes like this as to how things have altered the course of the epidemic," Dr Trauer said.
Professor Catherine Bennett, who holds the chair in epidemiology at Deakin University, said the ACT might have seen the first signs it was through the worst of the most recent wave and the hospitalisation numbers would level out and come down.
Professor Bennett said case numbers were unhelpful because the ascertainment rate - the number of infections detected - varied: when case numbers rose, more people would present for testing would capture a greater number of cases.
But a correlated downturn in case numbers and hospitalisation numbers was a positive sign, she said.
"I do think it looks like the ACT is leading the way out of this wave and the other states and territories will be really keen for that to be true," Professor Bennett said.
Fairer weather, along with greater booster vaccination take up and physical distancing would help bring the wave down faster and reduce pressure on the health care system, she said.
Dr Coleman used a filmed message on social media last week to say the COVID-19 wave would peak in the coming weeks in the territory.
"[There are] ongoing challenges for everyone in our community. From workforce issues affecting businesses and schools and demand growing on hospitals and health services every corner of our community is feeling the impacts of COVID-19 in some way," Dr Coleman said.
Dr Coleman encouraged Canberrans to take personal responsibility, wear a mask in crowded indoor spaces or environments where physical distancing was impossible and ensure they were up to date on their vaccinations.
"So while we have high COVID-19 numbers in our community, I strongly encourage everyone to follow COVID smart behaviours. These are the simple steps that we already know how to do but are more important than ever in reducing the impact of this new wave of COVID-19," she said.
Dr Coleman said on July 12 cases in the ACT could reach 2000 or 3000 a day by late July and early August.
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