Ontario now testing asymptomatic people for hantavirus; low-risk cases to stop isolating if negative

Nine people in Canada have been classified as “high-risk contacts” and are isolating in Ontario, Alberta and British Columbia, while 26 others have been deemed “low risk.”

Public health officials have described “low-risk” contacts as air passengers who were on the same flight as someone with hantavirus, but weren’t in close proximity to them.

The question of whether to test asymptomatic people has been raised several times over the past week, complicated by the long incubation period of the virus, and potential for symptoms to show up weeks after exposure.

Earlier this week, Jones said the guidance from the province’s top doctor was that it wasn’t appropriate to test people showing no symptoms at the time.

Dr. Joss Reimer, Canada’s chief public health officer, also suggested testing asymptomatic people might give a false sense of security.

“If somebody is perhaps testing negative, but later could go on to develop hantavirus, I don’t want that individual to be taking their isolation requirements less seriously. So that’s the balance that we’re trying to strike in getting as much information as we can and is useful without giving people a false reassurance that might lead to unnecessary exposures,” Reimer said at a press briefing Friday.

Canada has two kinds of hantavirus tests: one that detects antibodies in the blood, and a PCR test, which finds particles of the virus itself.

The World Health Organization said its international hantavirus case count is 10, as the previous tally had an inconclusive test in the U.S. that’s since been confirmed as negative.

Three people have died. No additional deaths have been recorded since May 2.

More cases may be reported internationally in the coming days, since it can take up to six weeks to develop symptoms, said Dr. Maria Van Kerkhove, WHO’s director of health emergency alert and response operations.

“This does not mean the outbreak is expanding. It shows that the control measures are working, that laboratory testing is ongoing, and that people are being cared for with support from their governments.”

On Friday, WHO held an emergency scientific consultation on Andes virus to discuss the latest research on transmission, diagnosis, treatment and vaccination.

Van Kerkhove said WHO is also working to better understand how this outbreak began and spread.

“The story of this outbreak, I think will be studied for years and years.”

– With files from Nicole Ireland

This report by The Canadian Press was first published May 15, 2026.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

Hannah Alberga, The Canadian Press

by The Canadian Press

Ontario now testing asymptomatic people for hantavirus; low-risk cases to stop isolating if negative

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