Canadian health authorities announced Tuesday that a teenager infected with H5N1 avian flu of unknown origin is in critical condition.

According to Bonnie Henry, British Columbia provincial health officerthe child suffered from acute respiratory distress and was hospitalized on Friday.

The teenager is the first suspected case of H5N1 avian flu in Canada.

“Our thoughts continue to be with this person and their family,” Henry said.

Authorities believe the virus was contracted from animal sources; however, the teen was not on a farm or near known wild birds or backyard poultry – common reservoirs of the disease.

Learn more: How was H5N1 avian flu introduced into the California dairy industry?

According to an interview with Henry by CBC, the teen had no contact with birds, but interacted with various other animals, including a dog, cats and reptiles, in the days before his illness. Tests carried out on these animals have so far been negative.

Health authorities are also tracing people the teen had contact with and have so far identified no other infections.

The situation is “horrible,” said Jennifer Nuzzo, director of the Pandemic Center at Brown University. “The idea that we have a child, a teenager, seriously ill from this virus is actually a real tragedy. But unfortunately, it’s not surprising, given everything we know about H5N1 and its potential pathogenic.”

She noted that since the late 1990s, when this current strain of bird flu emerged in China’s Guangdong province, the mortality rate has been close to 60%. That figure is likely exaggerated, she said, since most of the people tested for the disease were likely those who went to a hospital or clinic for treatment; people with mild or asymptomatic symptoms are unlikely to have been tested.

Nonetheless, Nuzzo said, while this virus could “be a lot less deadly than what we’ve seen so far,” it could still be a lot more deadly than any pandemic we’ve seen in a long time, including COVID.

She said the case concerned her for three reasons: The first is the seriousness of the teen’s illness. The second is that “we don’t understand how the teenager became infected,” she said. Her third concern is how government officials are handling this outbreak, which she describes as “letting it continue to spread from animals to humans, without trying to do more to get ahead of it.”

She said the virus may not end up becoming more virulent or more efficient at moving between people, “but I don’t think we want to wait and hope for that to happen.”

Since the virus emerged in North American wild birds in 2021, human cases have mostly presented as mild. Since 2022, there have been 47 human cases in the United States – 25 in dairy workers, 21 in poultry workers, and one case in Missouri whose source has not yet been identified.

However, a recent study from the US Centers for Disease Control and Prevention shows that the virus is more prevalent among dairy workers than previously thought. An examination of antibodies in 115 dairy workers in Michigan and Colorado showed that eight people tested positive for the disease, or 7% of the study population, indicating that either the workers were not reporting the disease or that they were asymptomatic.

Nuzzo also highlighted a recent study published in Nature, edited by Yoshihiro Kawaokaan H5N1 expert at the University of Wisconsin, Madison, who showed that the virus that infected the first reported dairy worker in Texas acquired mutations that made it more serious in animals and allowed it to move more efficiently between them – by air. breathing.

When Kawoaka exposed the ferrets to this viral isolate, 100% of them died. Additionally, it didn’t seem to matter how much virus they were initially exposed to. Even very low doses caused mortality.

Kawoaka told The Times in an interview that the mutations seen in this particular isolate have appeared elsewhere in past outbreaks in birds and mammals, “so in that sense, it’s a very orthodox mutation.”

Learn more: ‘More serious than we hoped’: Bird flu deaths rise among California dairy cows

The isolate from the Canadian teenager has not yet been genetically sequenced. We therefore do not know if he carries these mutations or others.

Fortunately, this isolate has not been observed since its appearance in this Texas dairy worker. It is unclear why the worker did not exhibit more serious symptoms.

However, there are some hypotheses.

Kawaoka’s research shows “inefficient replication” of the virus in human corneal cells. If the worker was exposed by splashing contaminated milk in the eye or rubbing the eye with a contaminated glove, the virus could have been blocked – unable to replicate as it might have if the worker had been exposed by inhalation.

Nuzzo said there are other hypotheses — which she said are just hypotheses — including that people who were exposed to the H1N1 swine flu outbreak in 2009 may have acquired some immunity against the “N1” part of the virus.

The other dates back to a person’s first exposure to the flu.

There is a scientific hypothesis called “original antigenic sin” which suggests that a person’s first exposure to a particular virus “might somehow set the tone” for that person’s immune system in the future – so the first exposure to This worker’s flu may have provided his immune system with the defenses necessary to suppress H5N1.

“There are a lot more questions than answers at this point. So there are a lot of interesting hypotheses about why the most recent cases have been mild, there’s not enough evidence to just rule out more than two decades of evidence on this virus that tells us it could be very deadly,” Nuzzo said.

As the human flu season picks up, Nuzzo said it’s extremely important that people do what they can to prevent the spread of the disease.

She said seasonal flu and H5N1 vaccines should be provided to dairy workers.

Unfortunately, she said, “our surveillance efforts to try to detect outbreaks on farms, while improving, still don’t come close to what we need to know about these outbreaks.”

In the meantime, vaccines and antiviral drugs must be available.

“News of a very serious human case of avian flu is a massive wake-up call that should immediately mobilize efforts to prevent another human pandemic,” said Andrew deCoriolis, executive director of Farm Forward. “We could have prevented the spread of bird flu on poultry farms across America, but we didn’t. We could have prevented the spread of bird flu on dairy farms, but we didn’t.”

“Industrial farms known for raising billions of sick animals in dirty, cramped conditions provide a recipe for viruses like avian influenza (H5N1) to emerge and spread,” deCoriolis said in a statement. “We are now on the cusp of another pandemic and the agencies charged with regulating farms and protecting public health are acting more slowly than the virus is spreading.”

As of Wednesday, 492 dairy herds had been infected with H5N1 in 15 states. More than half, 278, are in California. Two Oregon pigs were also infected.

This story was originally published in Los Angeles Times.