Bird flu is hitting the U.S. hard. Now, migratory birds are flying north

CBC

20-03-2025

Bird flu is at a dangerous point in the United States: Nearly 167 million birds have been impacted by the H5N1 strain since 2022, and 70 people have been infected. Now, birds are flying our way for the spring migration season.
A snow goose near Montreal, a great horned owl in southwestern Ontario, a Canada goose in Langley, B.C. — these are just some of the wild birds that have recently tested positive for H5N1 in Canada. But scientists are bracing for more, and are ramping up their efforts to monitor and curb the virus this season.
This winter has seen more outbreaks of H5N1 than usual, said Dr. Manon Racicot, a veterinary epidemiologist with the Canadian Food Inspection Agency (CFIA) in Saint-Hyacinthe, Que.
"Now that the birds are coming back north for the migration, we don't really know what's coming to us. Will the birds still be infected? Will they be shedding the virus in the environment in Canada?"
Adding to scientists' concern: Another strain of bird flu, H7N9, has been reported in a poultry farm in Mississippi, U.S. — a first since 2017. While it's not the dominant type of bird flu currently making the rounds in the U.S., H7N9 has a far higher death rate than H5N1, killing nearly 40 per cent of humans infected since it was detected in 2013. The infected birds have been killed, and the premises quarantined, said state authorities.
One mutation away
H5N1 has also crossed species, and adapted to mammalian hosts. Animals like seals, cats and dogs have died after mingling with wild birds, or eating raw pet food.
Dairy cows in the U.S. have been getting sick in droves, with 989 herds affected across 17 states, according to the Centers for Disease Control and Prevention.
Bird flu does not appear to be easily transmissible between people, for now. But the strain of H5N1 circulating in cows in the U.S. is just one mutation away from being more transmissible between humans, suggests a study recently published in the peer-reviewed journal Science.
And when it infects humans, the virus can be deadly. In January, a senior in Louisiana became the first H5N1-related human death in the U.S.
Canada's only known case of H5N1 was confirmed two months earlier, in November: a teenager in British Columbia who was hospitalized for two months. We still don't know how she was infected.
In both cases, genetic analysis suggested the virus had mutated to become more effective at attaching to cells in the upper respiratory tract.
All this has scientists and physicians on high alert.
"Quite frankly, a single case of avian influenza is very concerning because we do not want that virus to adapt to humans," said Dr. Danuta Skowronski, an epidemiologist at the B.C. Centre for Disease Control (BCCDC).
"We all have a responsibility to shut that down as rapidly as possible to contain it. That's a global effort. We are communicating globally with the U.S., with the U.K., with wherever we can to ensure we get the best possible knowledge."
Pulling out of WHO, scrambling to rehire employees
With how much the disease is changing in the U.S. right now, it's critical that American authorities continue communicating with other countries and the World Health Organization (WHO), says Ian Brown, a leading avian influenza expert at the Pirbright Institute in the U.K.
But the Trump administration is pulling the U.S. out of the WHO. It's also cutting funding and jobs at key agencies like the National Institutes of Health.
"We know it's a sensitive situation. We know some of our colleagues, they may be at risk of not having a job," said Brown.
It's early days, he says, but he fears there will be reduced information-sharing between American scientists and international counterparts.
"Early signs are that the interaction we've been used to having, successfully for many years, may now be compromised."
There have already been missteps.
The agriculture department has scrambled to rehire employees working on the bird flu response, after mistakenly firing them during its swift purge of the federal workforce, on the recommendations of Elon Musk's Department of Government Efficiency. They've been having trouble getting them back, Politico reported.
The WHO has already seen an impact on cuts for bird flu monitoring, sa id director general Dr. Tedros Adhanom Ghebreyesus on Monday.
Is the U.S. speaking with Canada on bird flu?
Thankfully, though, the U.S. is returning Canada's calls on human cases of bird flu, especially among those who work with infected poultry or dairy cattle, says Dr. Theresa Tam, Canada's chief public health officer.
"I think public health at every level is trying to really be very vigilant about cases in those different populations and we are sharing information on an ongoing basis," said Tam.
Canada relies on the U.S. to curb the virus effectively. On the animal health side, for instance, U.S. and Canadian officials work together to monitor bird flyways and keep a close eye on wild and domestic birds, sharing mutations of concern, as well as approximate locations of the infected birds.
On the provincial level, too, teams in British Columbia are keeping close contact with counterparts in states like Washington, Oregon and Alaska, said Dr. Bonnie Henry, B.C.'s provincial health officer.
"I think one of the things that helps us is the relationships we have, personal relationships."
Canada also keeps a close eye on our dairy cows: The CFIA tests samples of raw milk arriving at processing plants. So far, all samples have come back negative, as of Feb. 28.
Learning from COVID-19
But both Tam and Henry emphasize: it's important to beef up Canada's monitoring and be prepared, especially in case the virus changes and becomes more transmissible among humans, which could spark a pandemic.
Those efforts include "increasing monitoring and vigilance, laboratory testing, ensuring that any human case is getting investigated," said Tam.
Scientists at the BCCDC are among many in Canada already doing some of that preparatory work.
"Through the pandemic, we've learned a lot about tools that public health can use to make their decisions," said Linda Hoang, medical director of its public health laboratory.
The BCCDC is monitoring mutations that could make H5N1 more adapted to humans, developing antibody tests to monitor human exposure, and researching how bird flu is transmitted.
It's all information that could be critical for decision-makers should the virus become more transmissible.
Henry says she's confident — even if there are temporary bouts of silence from American counterparts — that Canadian surveillance is strong enough to keep a close eye on bird flu.