Outdoor transmission of COVID-19 is far lower than statistics suggest, expert says
TORONTO -- With the current-stay-at-home order expected to be extended until at least June in Ontario, infectious disease experts are urging officials to reopen outdoor amenities as the weather warms, pointing to the low risk of transmission outside.
On Tuesday, Dr. Peter Jüni, scientific director of Ontario's COVID-19 Science Advisory Table, said outdoor activities like golf, tennis and beach volleyball are low-risk. “Science is telling us that safe outdoor recreation is important,” Dr. Jüni said.
Under the current stay-at-home order, outdoor sports are not permitted across the province. The only outdoor recreational areas open are parks and playgrounds.
The Centre for Disease Control (C.D.C) has said “less than 10 per cent” of COVID-19 transmission has occurred outdoors, but Hamilton infectious diseases physician Dr. Zain Chagla said outdoor transmission is actually far lower than 10 per cent.
“I think that 10 per cent figure...is actually much, much closer to less than 1 per cent,” Chagla said.
In reality, Chagla said that “99 per cent of transmission is indoors. 0.1 per cent is outdoors.”
Within the “many studies” the C.D.C cites as evidence for the “less than 10 per cent” figure, the majority of outdoor transmission cases occurred at construction sites in Singapore. In one of the studies, 95 of 10,926 cases of COVID-19 were linked to outdoor transmission. And, all 95 of the cases occurred at the construction sites.
In the study, the construction sites were defined as “outdoor spaces,” but Dr. Chagla points out, these people would have been working in close proximity to one another. Layered on top of that, Singapore is an exceptionally humid environment, which could lead to gathering indoors as relief from the heat.
There is no data available in Canada or Ontario on outdoor transmission, but a study of case numbers in Ireland found that just one in every thousand confirmed COVID-19 cases was traced to outdoor transmission. Population wide, that means 0.1 per cent of total cases was linked to outdoor transmission.
At the onset of the third wave of the pandemic, British Columbia took a harm reduction approach, permitting outdoor gatherings of 10 people, keeping case numbers down, without imposing large scale outdoor restrictions.
Now, as the Victoria Day long weekend approaches in less than two weeks, Dr. Chagla says it’s time to start pivoting to an “outdoor focused strategy,” shifting gears from discouraging being outdoors to encouraging it.