What will mass testing reveal?
Little is known about how asymptomatic people spread COVID-19
As Hamilton public health ramps up testing in long-term care homes and puts one back in outbreak status, one medical expert says it’s too soon to say how and if mass testing will help stop spread.
Still, others have called for widespread testing and say it’s key to understanding transmission.
On Friday, Heritage Green Nursing Home in Stoney Creek, the site of the city’s first outbreak back in March, had the misfortune of finding itself back in outbreak status, four days after their initial outbreak was declared over.
The three new cases — all asymptomatic residents — were identified following mass testing at the long-term care home, as per provincial directive to test all long-term care residents and staff.
No one in the home is showing symptoms.
Dr. Dominik Mertz, an associate professor in McMaster University’s Division of Infectious Diseases, says it’s not clear yet what value there is in identifying asymptomatic patients in care homes.
“The assumption is (that) you do mass testing and pick up cases that wouldn’t have captured otherwise,” Mertz said.
“It’s possible those three (cases at Heritage Green) would have been a source of a new outbreak — or it may not be the case and then the risk is you put outbreak measures in place for something that wouldn’t have happened.”
Mertz said a great deal about the virus remains unknown, including how asymptomatic carriers spread the virus. It is known that presymptomatic carriers can spread the virus before showing symptoms, but there are also people who never show symptoms and questions remain about how and if they transmit infection, he said.
In addition, some people have tested positive weeks after contracting the virus, he said.
Therefore, the Heritage Green cases could fall into one of three categories: presymptomatic, asymptomatic or they caught the virus weeks ago but are still testing positive.
Without knowing if and how asymptomatic people can spread the virus, long-term care homes with asymptomatic cases are forced to put the home into a hard lockdown, isolating all residents.
“It makes sense to pull the trigger if you think you can prevent harm,” Mertz said. But in the current situation, when we don’t fully understand asymptomatic spread, “it may result in harm to the residents without any benefit.”
Still, other health-care experts have long pleaded with the province to test everyone in long-term care settings — a plea that fell on deaf ears until the province acquiesced on April 22.
And epidemiologists say testing is critical to understanding the extent of COVID-19’s spread, at least in the community.
“Testing is one of the tellers of epidemic response,” said Isaac Bogoch, an infectious disease expert based out of Toronto General Hospital, “and certainly widespread testing is essential in getting a better understanding of how the epidemic is affecting different communities and the province at large.”
Mertz says he would have preferred Ontario undertake a “formal assessment” of the potential value of mass testing before rolling it out provincewide. The undertaking is resource intensive, he added, at a time when resources are limited.
Meanwhile, the full extent of the second outbreak at Heritage Green isn’t yet known.
Public health says some residents are still awaiting test results. Staff testing starts Tuesday.