BRITISH COLUMBIA — One of four Canadians quarantining in British Columbia after exposure aboard the MV Hondius cruise ship has presumptively tested positive for hantavirus, the Public Health Agency of Canada confirmed. The individual, who is from Yukon, developed mild symptoms including fever and headache two days before the positive test result.

The patient and their spouse were hospitalized on Thursday in Victoria for assessment and testing and will remain in isolation at the hospital. The partner tested negative for hantavirus. A third individual who had been isolating in the same lodging was transferred to hospital for monitoring, while a fourth continues to isolate at home under daily observation. Samples from the patient have been sent to the national microbiology lab in Winnipeg for confirmatory testing, with results expected over the weekend.

"Clearly this is not what we hoped for, but it is what we planned for," said Dr Bonnie Henry, British Columbia provincial health officer. "The patient is stable, and their symptoms remain mild at this point." "And they are still in hospital, in isolation, being monitored and receiving care as needed," she said.

The four Canadians arrived in Victoria on 10 May, were assessed with no symptoms on arrival, and were transferred to lodging for a minimum 21-day quarantine. The World Health Organization has recommended a 42-day quarantine period for hantavirus exposure. The four have had no contact with the public since arriving in Canada.

Of six Canadians who were on the MV Hondius, two are self-isolating at their home in Ontario. Two couples, one from British Columbia and one from Yukon, are isolating on Vancouver Island. None of the other five Canadians have tested positive so far. Canadian health officials are tracking 36 people currently in isolation, including four cruise ship passengers.

"The overall risk to the general population in Canada from the Andes hantavirus outbreak linked to the MV Hondius cruise ship remains low at this time," the Public Health Agency of Canada said.

The case brings the total number of hantavirus infections linked to the vessel to 11, all among cruise passengers. Since 11 April, three people who were on board have died of suspected hantavirus infection, including a Dutch couple and a German woman, with two of the deaths confirmed as hantavirus infections.

The MV Hondius set sail from Argentina on 1 April and docked in Tenerife in Spain's Canary Islands less than a week before passengers were evacuated. The ship had 147 passengers and crew from 23 countries on board during the outbreak.

Hantaviruses are usually carried by rodents, and human transmission of the Andes strain is possible, according to the World Health Organization. Symptoms of Andes hantavirus can include fever, extreme fatigue, muscle aches, stomach pain, vomiting, diarrhea, and shortness of breath. There were no known cases of hantavirus in the United States as of Friday.