A B.C. teen has a suspected case of H5N1 avian flu B次元官网网址� the first known human to acquire the virus in Canada.

The provincial government said on the weekend that B.C.B次元官网网址檚 chief veterinarian and public health teams are still investigating the source of exposure, but that itB次元官网网址檚 B次元官网网址渧ery likelyB次元官网网址� an animal or bird.

Human-to-human transmission is very rare, but as cases among animals rise, many experts are worried the virus could develop that ability.

The teen was being treated at BC ChildrenB次元官网网址檚 Hospital on Saturday. The provincial health officer said there were no updates on the patient Monday.

B次元官网网址淚B次元官网网址檓 very concerned, obviously, for the young person who was infected,B次元官网网址� said Dr. Matthew Miller, director of the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University in Hamilton, Ont.

Miller, who is also the co-director of the Canadian Pandemic Preparedness Hub, said there have been several people infected with H5N1 in the U.S.,and almost all were livestock workers.

In an email to The Canadian Press on Monday afternoon, the Public Health Agency of Canada said B次元官网网址渂ased on current evidence in Canada, the risk to the general public remains low at this time.B次元官网网址�

WHAT IS H5N1?

H5N1 is a subtype of influenza A virus that has mainly affected birds, so itB次元官网网址檚 also called B次元官网网址渂ird fluB次元官网网址� or B次元官网网址渁vian flu.B次元官网网址� The H5N1 flu that has been circulating widely among birds and cattle this year is one of the avian flu strains known as Highly Pathogenic Avian Influenza (HPAI) because it causes severe illness in birds, including poultry.

According to the World Health Organization, H5N1 has been circulating widely among wild birds and poultry for more than two decades. The WHO became increasingly concerned and called for more disease surveillance in Feb. 2023 after worldwide reports of the virus spilling over into mammals.

HOW COMMON IS INFECTION IN HUMANS?

H5N1 infections in humans are rare and B次元官网网址減rimarily acquired through direct contact with infected poultry or contaminated environments,B次元官网网址� the WHOB次元官网网址檚 website says.

Prior to the teen in B.C., Canada had one human case of H5N1 in 2014 and it was B次元官网网址渢ravel-related,B次元官网网址� according to the Public Health Agency of Canada.

As of Nov. 8, there have been 46 confirmed human cases of H5N1 in the U.S. this year, the Centers for Disease Control and Prevention says. There is an ongoing outbreak among dairy cattle, B次元官网网址渟poradicB次元官网网址� outbreaks in poultry farms and B次元官网网址渨idespreadB次元官网网址� cases in wild birds, the CDC website says.

There has been no sign of human-to-human transmission in any of the U.S. cases.

But infectious disease and public health experts are worried that the more H5N1 spreads between different types of animals, the bigger the chance it can mutateand spread more easily between humans.

WHAT ARE THE SYMPTOMS OF H5N1?

Although H5N1 causes symptoms similar to seasonal flu, such as cough, fever, shortness of breath, headache, muscle pain, sore throat, runny nose and fatigue, the strain also has key features that can cause other symptoms.

Unlike seasonal flu, most of the people infected in the U.S. have had conjunctivitis, or B次元官网网址減ink-eye,B次元官网网址� said Miller.

One reason for that is likely that many have been dairy cattle workers.

B次元官网网址淎t these milking operations, itB次元官网网址檚 easy to get contamination on your hands and rub your eyes. We touch our face like all the time without even knowing it,B次元官网网址� he said.

B次元官网网址淎lso, those operations can produce droplets or aerosols, both during milking and during cleaning that can get into the eye relatively easily.B次元官网网址�

But the other reason for the conjunctivitis seen in H5N1 cases is that the strain binds to receptors in the eye, Miller said.

While seasonal flu binds to receptors in the upper respiratory tract, H5N1 also binds to receptors in the lower respiratory tract, he said.

B次元官网网址淭hatB次元官网网址檚 a concern B次元官网网址� because if the virus makes its way down there, those lower respiratory infections tend to be a lot more severe. They tend to lead to more severe outcomes, like pneumonias for example, that can cause respiratory distress,B次元官网网址� Miller said.

WILL THE FLU VACCINE PROTECT AGAINST H5N1?

We donB次元官网网址檛 know B次元官网网址渨ith any degree of certainty,B次元官网网址� whether the seasonal flu vaccine could help prevent infection with H5N1, said Miller.

Although thereB次元官网网址檚 no data yet, itB次元官网网址檚 quite possible that it could help prevent more severe disease once a person is infected, he said.

ThatB次元官网网址檚 because the seasonal flu vaccine contains a component of H1N1 virus, which B次元官网网址渋s relatively closely related to H5N1.B次元官网网址�

B次元官网网址淪o the immunity that might help protect people against H5N1 is almost certainly conferred by either prior infection with or prior vaccination against H1N1 viruses that circulate in people,B次元官网网址� Miller said.

HOW ELSE CAN I PROTECT MYSELF?

The Public Health Agency of Canada said as a general precaution, people shouldnB次元官网网址檛 handle live or dead wild birds or other wild animals, and keep pets away from sick or dead animals.

Those who work with animals or in animal-contaminated places should take personal protective measures, the agency said.