What we know about Hantavirus now that people have returned to Canada

The hantavirus outbreak aboard the MV Hondius cruise ship has raised concerns among Canadians and prompted many questions. Here is what is known so far.

Passengers aboard the ship contracted the Andes virus, found in Argentina and Chile. It is the only known hantavirus, among dozens of strains, capable of spreading from person to person. Hantaviruses originate in rodents, including mice and rats.

Ten people connected to the outbreak are currently in Canada, including six passengers and four people who were not on board but may have been exposed to the hantavirus during flights.

Four passengers are isolating on Vancouver Island: a Yukon couple in their 70s, a person in their 70s from the island, and a person in their 50s from British Columbia who now lives abroad.

Dr. Bonnie Henry, British Columbia’s provincial health officer, said Monday that their 21-day quarantine period began Sunday but could be extended to 42 days.

Two other passengers, also a couple, are isolating in Ontario’s Grey Bruce region and are being monitored for 45 days.

One visitor to Canada was not aboard the ship but travelled on a flight with a passenger who later died from hantavirus. That person is isolating in Ontario’s Peel Region.

Two other travellers may also have been exposed during a flight and are isolating at home in Alberta for at least 21 days from the date of possible exposure.

A Quebec resident who may have been exposed on another flight was in isolation until Monday, when Quebec’s Health Department said the person was considered a low-risk contact and could self-monitor for 42 days.

Quebec’s Health Department said Wednesday that eight people in the province may have been exposed, but the risk of developing an infection was considered very low. Officials said they did not need to isolate unless symptoms developed.

Ontario’s Health Ministry said Tuesday afternoon it had asked seven additional people to isolate, even though they were considered low risk, because they had contact with someone at higher risk.

British Columbia health officials said Wednesday they had not identified any low-risk contacts in the province and that no one other than the four cruise ship passengers was isolating or under monitoring.

Alberta health officials also said they were not considering any additional people to have been potentially exposed.

Incubation Period

Hantaviruses are known to incubate for up to eight weeks, although that is unusual. On average, symptoms typically appear two to three weeks after exposure, said Bryce Warner, a hantavirus scientist with the University of Saskatchewan’s Vaccine and Infectious Disease Organization.

The World Health Organization recommends a 42-day quarantine period because of the virus’s long incubation period.

However, the organization says each jurisdiction should determine the appropriate quarantine period based on the risk level of returning individuals and whether they had direct contact with sick passengers.

The Public Health Agency of Canada said passengers and crew who were aboard the ship, as well as anyone identified as a high-risk contact from a flight with a confirmed case, should not travel.

The federal government announced Tuesday temporary measures preventing passengers and crew who were aboard the MV Hondius since April 1 from boarding flights to Canada.

The agency said the decision is based on WHO recommendations and that it is working with public health authorities, airlines and border services.

Canada has two types of hantavirus tests: a blood antibody test and a PCR test that detects viral particles.

However, because of the virus’s long incubation period, experts question how useful testing is for someone without symptoms.

Public health officials said none of the 10 potentially exposed people in Canada had developed symptoms.

“The question will always be whether the person is truly negative because they were never infected, or whether they are negative because, at the time of testing, the viral load was too low to detect,” said David Safronetz, head of special pathogens at the National Microbiology Laboratory in Winnipeg.

“That is exactly what public health agencies around the world are dealing with right now: determining the best approach,” he added.

Safronetz said people would be tested once symptoms appear. Provincial laboratories would conduct the tests before sending samples to the national laboratory for confirmation.

The illness caused by the Andes virus, called hantavirus pulmonary syndrome, often begins with very general symptoms such as fatigue, fever or gastrointestinal issues.

That means that even if someone under monitoring in Canada begins to feel ill, it may not necessarily be hantavirus.

“Hantaviruses are tricky, right? The early symptoms can easily be mistaken for a cold, a headache or even stress,” Safronetz said. “These people are under a great deal of stress right now. They have gone through a difficult period. We have to take all of that into account in the testing strategies being used.”

Hantavirus pulmonary syndrome typically progresses rapidly to acute respiratory distress after the initial symptoms appear. The fatality rate is about 30 per cent.

Treatment

There are no antiviral medications that directly treat the disease.

Treatment mainly involves supportive care, including pain management, maintaining hydration and respiratory support, including the use of ventilators if necessary, according to the World Health Organization.

Human-to-human transmission of hantavirus is rare, experts say.

Doctors, scientists and public health officials stress that close and prolonged contact, such as the conditions aboard a cruise ship, is required for person-to-person transmission.

“This is not the next pandemic. I think that’s the key message for everyone: this is not COVID-19,” Safronetz said.

He added that Canada already has a hantavirus known as Sin Nombre virus. It is not known whether it can spread between humans, but a small number of Canadians contract it each year through contact with mouse droppings.

U.S. scientists developed a vaccine several years ago, Warner said, but it has not undergone large-scale clinical trials.

Some Canadian laboratories, including Warner’s, are also working on hantavirus vaccines, though research remains in the early stages of animal testing.

“The long-term goal, of course, is to develop a vaccine that can eventually be approved and administered to humans. We are still far from that point,” he said.

–This report by La Presse Canadienne was translated by CityNews