British Columbia’s top doctor says the four passengers returning home from the hantavirus-hit cruise ship remain in a “critical period,” but stressed she would not call them “patients” as they are not considered infected.

Henry told reporters they will be monitoring the four passengers, ensuring they are cared for during the minimum isolation period of 21 days.

“We know as well the incubation period of this strain of the virus can be as long as six weeks, so we’re at actually a critical period,” she said. “We know the median incubation period is about 15 to 18 days, so we’re still in a period of time when we may see more cases arise.”