No evidence to support outdoor mask-wearing rule, scientists say

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As Melbourne emerges from two weeks of lockdown, experts have cast doubt on the science being used to retain rules such as the 25-kilometre travel bubble and the wearing of masks outdoors.

Victoria recorded no new local cases for the first time in almost three weeks on Friday as the city’s coronavirus restrictions eased.

Melbourne’s outdoor masks rules did not change on Friday.Credit:Getty

Acting Premier James Merlino said zero fresh cases was the “news I know everyone in Victoria wanted to hear” but the return of “doughnut days” brought a warning that the current outbreak was not over.

“The week ahead probably won’t be all zero cases,” Chief Health Officer Brett Sutton said. “We have thousands of primary close contacts, some of who will become positive.”

The outbreak may not be at an end but the easing of Melbourne’s lockdown means the city is no longer a “hotspot” and federal support payments for people who have lost work will cease.

Federal Treasurer Josh Frydenberg revealed on Friday that 50,000 people had applied for payments with more than 34,000 already processed.

QUT Professor Lidia Morawska, director of the International Laboratory for Air Quality and Health.

Professor Morawska has been a leading global voice behind the belated recognition from the World Health Organisation and other international health authorities of the role airborne transmission played in COVID-19.

“There is no evidence the concentration of virus in any open space would be any risk of infection,” she said.

“In my view, requiring masks outdoors at every place is a bit misguided, because people stop being compliant, because it does not make sense.”

Professor Morawska said people should wear masks outdoors when they could not maintain a safe distance, such as stopping for a chat or standing in line.

Brett Sutton, Victoria’s Chief Health Officer.Credit:Nine News

Chief Health Officer Brett Sutton said on Friday that masks remain a “really important intervention”.

“People move in and out of indoor and outdoor areas all the time, and it is not always easy to judge how close others are,” he said.

“It will, especially if both individuals are wearing a mask at the same time, reduce the transmission risk. And transmission does happen outdoors.”

A study that has not yet been peer-reviewed, co-authored by Deputy Chief Health Officer Allen Cheng and funded by the Victorian government, found masks were the most-effective measure that brought Victoria’s second wave under control.

A Health Department spokesman said that while outdoor transmission is substantially less likely than indoor, “globally we have seen super-spreader events occurring outdoors, so it remains a risk”.

But experts say that masking indoors and outdoors are fundamentally different propositions.

In a meta analysis of five papers on COVID-19 and seven on influenza or similar viruses, researchers found less than 10 per cent of transmission reported were outdoors; the researchers themselves think that estimate is too high, as they counted cases at construction sites or summer camps where people shared bunks.

Irish health authorities tracked 232,164 cases and were able to trace just 0.1 per cent to outdoor transmission.

“Transmission is 20 times less outdoors, and when you’ve got very few cases in the community you’re talking about a minuscule benefit,” said Hassan Vally, associate professor in epidemiology at La Trobe University.

Professor Peter Collignon, a member of the federal government’s infection control expert group told Neil Mitchell on 3AW radio on Friday that he could not see “a lot of extra benefit” from insisting people wear masks outside.

“The bottom line is if you look at other states, Sydney, etc, they have managed to get these things under control when they’ve had numbers less than [the Commonwealth hotspot definition of 10 cases] per day without city-wide restrictions and lockdown.”

Wes Lambert, chief executive of the Restaurant and Catering Industry Association, said the number one thing outdoor masking did was remind people of the risk of COVID-19.

“This weekend could have been an opportunity to jump start many hospitality businesses after two weeks of lockdown,” he said. “Instead the added restrictions may serve to stop Victorians going out at all.”

Under the new restrictions, indoor seated entertainment venues can reopen for up to 50 people.

That meant Melbourne’s IMAX cinema reopened on Friday, but the next-door Melbourne Museum remained closed, as did the Bunjilaka Aboriginal Cultural Centre, Immigration Museum and Scienceworks.

“It does not make sense at all. If you’re in a cinema, sitting for two hours, and if ventilation is not good, potentially the virus concentration can accumulate, you can inhale enough of it in that setting,” said Professor Morawska.

Staff at Kirks Wine Bar in the city put tables out in preparation to resume trading on June 11, 2021 in Melbourne.Credit:Darrian Traynor/Getty Images

In a museum people continually move through the space, reducing the potential level of exposure to an infectious person, she said.

Gyms remain closed, with international evidence that they have been the site of super-spreading. In one case, an ill fitness instructor in Hawaii spread COVID-19 to almost his entire class after they spent an hour cycling in a closed room.

“Gyms are a high-risk environment. We have had significant outbreaks in gyms. I think we had 27 cases in a gym,” Professor Sutton said on Wednesday.

This may be because people working out tend to breathe more heavily, pumping out infectious particles, and wander across the entire gym. Gyms also tend to be in enclosed spaces and with lots of shared facilities such as change rooms.

Victoria’s new restrictions also include a 25-kilometre travel limit, designed to curb an infected case’s contacts with people across the state.

“There is no evidence that I know that suggests restricting movement to 25 kilometres will cause more overlap in exposure sites and minimise contact tracing workload,” said Professor Catherine Bennett, chair of epidemiology at Deakin University.

“Cases and exposure sites will be clustered closer together, but I’m not sure that changes much and doesn’t apply to essential workers.”

Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.

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