It'll take up to 6 weeks to find out if anti-racism protests caused a spike in COVID-19 cases: researcher

Recent protests across B.C. in support of Black Lives Matter and defunding police forces have not led to a spike in COVID-19 cases so far, but one expert says that doesn't mean it won't happen.

An estimated 3,500 people attended one protest in Vancouver on May 31. Three weeks later, B.C.'s cases have continued to trend downward.

Thousands more took to the streets of Vancouver on Friday for the Freedom March to mark Juneteenth, the day that commemorates the end of slavery in the U.S.

But it's still too early to conclude the protests were safe, said Caroline Colijn, a Canada 150 Research Chair in mathematics for evolution, infection and public health at Simon Fraser University.

The incubation period of COVID-19 is 14 days, but not everyone who gets infected by the novel coronavirus that causes the illness has symptoms, Colijn says. Also, there can be delays in testing and some people might not get tested at all. 

"All of those factors mean it really is more than three weeks before we start seeing rises in case counts," she said. 

"Right now, from reported cases, it's really sort of a three- to six-week delay before we start seeing rises and we won't necessarily know unless we really interview people and ask them whether it was the protests."

There's a lot that's still unknown about COVID-19, Colijn said, including just how effective non-medical masks are and the differences between transmission indoors and outdoors.

Many of the worst outbreaks in the province have been in settings where people were sharing meals, talking and singing.

That's because COVID-19 is primarily spread through droplets. There's also a higher chance of spreading droplets when shouting, she added, but there's also a higher chance you'd encounter them indoors than outdoors, where they might be carried away in the wind.

Non-medical masks — which many people wore while attending protests in Vancouver — can act as a barrier against larger droplets.

Provincial Health Officer Dr. Bonnie Henry has asked anyone who attends a protest to monitor themselves for symptoms of COVID-19. Anyone who shows symptoms is asked to self-isolate and get tested.

"I encourage anyone who might be demonstrating to also please continue to keep that safe distance, to recognize the importance of making sure that we are not allowing this virus a chance to spread," Henry said earlier this month. 

Colijn says everyone should remain cautious around crowds and as the province continues to reopen.

Wearing a mask and physically distancing from other people is still the best way to protect yourself, she said.

"Those are still the best tools we have against this virus. We don't have a vaccine, we don't have a great treatment, we have some therapeutic promises but not anything that would say, 'Oh yeah, let's go back to normal, it's all good,'" she said. 

"Only one tool that we know worldwide has worked is staying away from each other."