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Most health experts have backed Victoria’s “circuit-breaker” five-day lockdown but some epidemiologists are “cautious” about Daniel Andrews’ claims regarding the UK variant at the centre of the Melbourne outbreak.
The B117 variant, which is thought to be 30-70% more infectious, has spooked health authorities around the world and is now ravaging the UK.
The Victorian premier said on Friday an outbreak of the UK variant that leaked from hotel quarantine meant the state would have to endure a five-day lockdown to try to prevent “a third wave”.
Notably, Andrews suggested contact tracing in response to the UK variant could become “impossible” because those who were contracting the virus were passing it on to others more quickly.
Explaining the decision to lock down the state while defending the contact tracing program, Andrews said: “Right now, we are reaching close contacts well within the 48-hour benchmark.
“But the time between exposure, incubation, symptoms and testing positive is rapidly shortening,” the premier said. “So much so, that even secondary close contacts are potentially infectious within that 48-hour window.”
Prof Catherine Bennett, the chair of epidemiology at Deakin University, said the UK variant was “more efficient” in that if it “gets the opportunity to infect someone, it’s more likely to do that”.
“That might, on average, make it a bit faster,” she said.
But Bennett stressed she was not aware of “evidence globally for a shorter average incubation period” for the UK variant. “And certainly not really rapid turnaround time between cases,” she said.
Bennett said she was “not convinced” and nothing she had seen suggested the current outbreak was “outside the realms of what we know about other variants”. “Globally, no one has talked about a shorter incubation period,” she said.
Hassan Vally, an epidemiologist and associate professor in public health at La Trobe University, said he was not “questioning” the claim the UK variant had a shorter incubation period but was “cautious” about “accepting it as fact”.
“It’s definitely more plausible that it would have a shorter incubation time,” he said. “If it’s more infectious, it binds to the cells better. That leads to it replicating more quickly. That lines up.”
Prof Adrian Esterman, an ex-World Health Organization epidemiologist at the University of South Australia, said globally there had been “several reports of it happening” but “we don’t know whether it’s a true shorter incubation period or just the circumstances of that particular outbreak”.
Prof Sarah Palmer, co-director of the Centre for Virus Research at the Westmead Institute for Medical Research, said it was acknowledged the UK variant was far more infectious.
“That means the mutations that have happened in this virus has allowed the virus to be pulled in closer to the cells that it targets and makes it much easier for the virus to infect those cells,” she said.
“If it can infect the cells quicker, then yes, it would be that people would be showing symptoms much faster as they’re infected.”
Palmer said the premier’s comments were “plausible” but “I’m not sure it’s been proven”.
Friday’s snap lockdown, which began just before midnight, was prompted by an outbreak at the Holiday Inn hotel quarantine site, which has now reached 13 cases.
The latest confirmed infection was in a worker at Brunetti’s cafe at Terminal 4 of Melbourne airport. The person had worked at the venue on 9 February and the entire terminal was now classified as an exposure site.
Prof Brett Sutton, Victoria’s chief health officer, said due to the variant involved people who were becoming symptomatic and then tested positive had “already infected their close contacts”.
While Bennett questioned the snap lockdown, Vally, Palmer and Esterman said they supported the move.
Vally said it didn’t matter what the reason was for the assessment that authorities were “lagging behind transmission”. A lockdown was the “obvious course of action”, he said. “That issue will be resolved in due time, whether it is some unique characteristic of that strain.”
“For me, it doesn’t matter scientifically proving beyond doubt that there’s a shorter incubation period time, the reality is that this assessment has been made that they just can’t get ahead of the virus,” he said.
“I accept that, and that’s enough justification to go down this path based on the precautionary principle. It’s better to endure five days of pain now than find we’ve had hundreds of cases in a week’s time.”
Esterman also backed the lockdown. “If it had been the usual variant, the one that has been floating around Australia for a year, I would say it was overkill,” he said. “But because it’s the UK variant I fully agree with the lockdown,” he said.
He noted some studies had also suggested the UK variant was more deadly.
While Bennett said there was no doubt the outbreak was a concern and the UK strain was a “nasty variant”, she questioned whether the response was “proportionate”.
“We could have introduced other restrictions to suppress the chances of spread,” she said.
“You might still close bigger gatherings, you might stop people having people to their home. But to go to full lockdown is an extreme measure, which is hard to see from what was presented to us today as the justification.”
Bennett said up to now the government’s response to the outbreak had been good, though hampered by finding out about some cases later due to people who delayed getting tested.
Source: The Guardian
Keyword: Epidemiologists back Victoria’s lockdown but say evidence not yet in on ‘shorter incubation’ | Victoria