Unclear if hantavirus tests always useful: experts

Health experts say it's not clear whether it's useful to test people who may have been exposed to hantavirus but don't have symptoms. 

Dr. Bonnie Henry, British Columbia's provincial health officer, says public health officials around the world are discussing the issue as passengers from a hantavirus-stricken cruise ship have returned to their home countries.  

She says tests for some viruses aren't effective before patients develop symptoms and little is known about how well testing works in rare cases of hantavirus. 

Henry says if any of the 10 people in Canada who may have been exposed to the virus develop symptoms, health officials are ready to test and treat them. 

She says there are two types of blood tests for hantaviruses — one that checks for antibodies and a PCR test that detects pieces of the virus itself.  

University of Saskatchewan hantavirus scientist Bryce Warner says health officials are in a "unique" situation because doctors wouldn't normally have any reason to suspect the rare virus until a patient is showing signs of illness. 

Warner, who works at the university's Vaccine and Infectious Disease Organization, says a negative test in someone without symptoms wouldn't necessarily mean they don't have hantavirus. 

"Because the incubation period can be several weeks, if you did a test in the first week and it was negative by PCR you can't just say 'OK I'm negative.' It could take another week or two or three really for that to come up as positive," he said. 

The number of positive cases internationally has grown since the evacuation of the MV Hondius ship Sunday on an island in Spain’s Canary Islands. On Monday, American and French officials confirmed two more people had Andes virus — the type of hantavirus that hit the ship and the only kind known to spread person-to-person.

That brings the total number of deaths to three and cases to seven, the World Health Organization said Monday.

Public health officials and infectious disease physicians have stressed that Andes virus spread between people requires close and prolonged contact and that it is not a pandemic threat.  

This report by The Canadian Press was first published May 12, 2026.

— With files from Hannah Alberga

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

By Nicole Ireland | Copyright 2026, The Canadian Press. All rights reserved.