Health experts say it's not clear whether testing people who may have been exposed to hantavirus but don't have symptoms is useful. The issue has become urgent as passengers from a hantavirus-stricken cruise ship have returned to their home countries.
Dr. Bonnie Henry, British Columbia's provincial health officer, explains that 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. She notes that 10 people in Canada may have been exposed to the virus.
Two types of blood tests exist for hantaviruses: one that checks for antibodies and a PCR test that detects pieces of the virus itself. However, Bryce Warner, a hantavirus scientist at the University of Saskatchewan's Vaccine and Infectious Disease Organization, warns that 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," Warner said.
Warner notes that 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.
The outbreak began with the evacuation of the MV Hondius ship on Sunday from an island in Spain's Canary Islands. The virus involved is Andes virus, the only type of hantavirus known to spread person-to-person. As of Monday, the total number of deaths reached three and cases reached seven globally, according to the World Health Organization.
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. If any of the 10 exposed Canadians develop symptoms, health officials are ready to test and treat them.
