Worried about bird flu? Here’s what you need to know

Over the past few years, a highly contagious strain of avian flu has swept around the world. It has caused mass die-offs of seabirds and sea lions, devastated poultry flocks in B.C. and infected dairy cows across the U.S. 

While it’s rare for people to contract bird flu, there are growing concerns about the potential for the virus to spark a human pandemic. Fifty-five cases of the virus have been confirmed in people in the U.S. this year — most after exposure to infected cattle or poultry. 

Canada confirmed its first case of a person contracting avian flu domestically in November, after a B.C. teenager was admitted to hospital. But public health officials have not been able to determine the exact source of the teen’s infection, despite an extensive investigation. As of last week, officials had still not been able to speak with the teen, who remained in critical condition in hospital. 

While the teen was infected with H5N1, the same strain of avian flu circulating in wild birds and poultry, a closer look at the whole genome sequence shows the teen’s infection was not directly linked to ongoing outbreaks at dozens of poultry farms, provincial health officer Bonnie Henry recently told reporters. She said the closest match for the teen’s virus was detected in two wild geese found dead in the Fraser Valley in October.

“It wasn’t a direct match. So that tells us as well that there may have been an intermediary, either another bird or an animal, between the geese that were detected and this young person,” Henry said. She also noted there is no evidence the virus passed from the teen to any other person. 

“So far this H5N1 virus, the avian flu virus, does not seem to transmit to people very well,” Henry said. She noted B.C. has not seen infections among poultry workers and workers euthanizing infected poultry flocks, who wear protective equipment but have also been exposed to high doses of the virus.

But Henry cautioned she is “very aware of the pandemic potential” of the virus. The more people and mammals exposed to bird flu, the greater the risk it changes in ways that make it easier to spread between people, she explained.

“We need to be vigilant for that and we need to take those measures that protect us individually and as a community,” Henry said. U.S. federal officials have said they plan to double emergency avian flu vaccine stockpiles, Wired reported in early October. Health Canada has approved three vaccines that could be used in the event of a pandemic and has an agreement in place with a manufacturer for domestic production if needed, The Canadian Press recently reported.

People can become infected if they inhale the virus or it gets into their mouth, nose or eyes. There’s no evidence that people can get infected by eating thoroughly cooked eggs or poultry or by drinking pasteurized milk, according to the Public Health Agency of Canada. However, the virus has recently been detected in unpasteurized milk in the United States. 

Henry cautioned people to avoid sick birds and animals, keep pets away from birds and out of ponds and marshy areas, avoid handling ducks, geese or poultry in places like petting zoos and to wash their hands after handling pets that have been outside. 

What else should we know about avian flu? Read on.

Why has bird flu become such a problem in the past few years?

There are many different strains of avian influenza. The H5N1 strain was first detected in 1996 in domestic waterfowl in China. In the following decades, it spread across Asia and into Europe and Africa, morphing into new forms. In 2021, a new, highly contagious H5N1 virus emerged and spread rapidly around the world. It was first detected in Canada in December 2021.

Hundreds of people around the world have been infected with H5N1 since 2003, and about half have died.

Over the past few years, the virus has devastated poultry flocks around the world and infected wild birds, sea mammals and dairy cows.

According to the Canadian Food Inspection Agency, 63 farms in Canada are currently infected with H5N1 and 54 of them are in B.C. Since 2022, more than seven million farmed birds in B.C. have died from infection or been culled because of the virus.

Why is avian flu infecting more poultry farms in B.C. than other provinces?

While avian flu has been detected in every province and territory, B.C.’s poultry farms have been the hardest hit in Canada. One reason could be that B.C. has a high concentration of poultry farms in the same region that offers prime winter habitat for migratory birds — the Fraser Valley.

“It creates this really high risk situation for spillover from wild birds into poultry,” B.C.’s deputy chief veterinarian Chelsea Himsworth explained in an interview with The Narwhal.

Many bird species, particularly migratory waterfowl, spend their summers in the Arctic. As they intermingle, so do the viruses they carry, which can lead to new seasonal strains of bird flu. In the fall, when the birds migrate south, they bring those mutated viruses with them, Himsworth said.

“The Fraser Valley is really the first big rest stop on that southerly migration,” she said. “That’s why we see these spikes or waves that consistently happen in that sort of October to December timeframe.”

How is B.C. monitoring for bird flu?

Every two weeks during the high-risk period from October to December, the province collects sediment samples from wetlands used by migratory birds to test for avian flu and track the spread of the virus, Himsworth said. “These wild birds, the majority of them actually don’t get sick and die from this virus, they shed it in their feces — and wetlands are Mother Nature’s outhouse,” she said.

Himsworth said record levels of avian flu have been detected in wetlands used by migratory birds in the Fraser Valley this year.

The latest sampling data on the B.C. avian flu wildlife and environmental surveillance dashboard, from early November, shows the high pathogenic virus responsible for the global outbreak was detected in sediment samples from the Reifel Migratory Bird Sanctuary on the Fraser River estuary and at Sardis Pond in Chilliwack, B.C.

Investigating problems. Exploring solutions

The Narwhal’s reporters are telling environment stories you won’t read about anywhere else. Stay in the loop by signing up for a weekly dose of independent journalism.

SUBSCRIBE

Investigating problems. Exploring solutions

The Narwhal’s reporters are telling environment stories you won’t read about anywhere else. Stay in the loop by signing up for a weekly dose of independent journalism.

SUBSCRIBE

While environmental surveillance offers “situational awareness,” Himsworth said the virus degrades in the environment, so scientists are only able to collect fragments of it from sediment samples. It’s enough to determine whether the virus is the same highly pathogenic avian flu causing the global outbreak, but not enough to determine the whole genome sequence. That sequence is important for understanding linkages between outbreaks on poultry farms and the virus circulating among wild birds, she said.

Scientists need to collect samples from infected birds to obtain the whole genome sequence. For now, that means waiting for birds to die, and then for someone to spot and report them, so scientists can pick them up and test them, Himsworth said.

Since 2022, the virus has been detected in B.C. in about three dozen species — mostly birds but also skunks and red foxes. So far this year, it’s been detected in cackling geese, Canada geese and snow geese, red-tailed hawks, a barred owl and a peregrine falcon as well as a number of other bird species.

Himsworth cautioned the dead birds that get reported don’t offer a clear picture of the species infected by the virus. Some species might be more likely to die from the virus or they might be more conspicuous on the landscape once they’ve died, because of their size. That’s why B.C. is also looking at potentially conducting more active surveillance by catching live birds or by testing samples from hunted birds.

“We’re essentially trying our best to see what picture the puzzle is creating with only a small number of pieces,” she said.

What impact has avian flu had on wild birds and other animals?

Across Canada, the H5N1 virus has been detected in about 100 species, from Atlantic puffins and bald eagles to green-winged teals and trumpeter swans, according to the national dashboard for avian flu in wildlife. While mostly detected in birds, the virus has also been found in harbour seals, two black bears and a white-sided dolphin.

“This virus does seem to be able to spread in wild birds and migratory birds without actually killing to a great extent, so we don’t have a good sense of which birds survive and which birds die really quickly, [and] a lot of that research is still ongoing,” Damien Joly, a wildlife epidemiologist and CEO of the Canadian Wildlife Health Cooperative, told The Narwhal.

But there are cases where the virus has taken a clear toll. H5N1 killed an estimated 25,000 northern gannets — white seabirds with black-tipped wings, yellow heads and striking blue skin around their eyes — in eastern Canada in 2022, Joly said. That adds up to about 11.5 per cent of North America’s breeding population of northern gannets.

“When you see the animals that are breeding dying, that’s when it has population effects,” Joly said.

In a statement, a spokesperson for Environment and Climate Change Canada said there are instances of mass mortality events that can be traced to highly pathogenic avian influenza in wild bird populations, although the scale and frequency has changed over time.

The spokesperson said preliminary results from Environment Canada’s sampling of birds captured live or harvested by hunters show the positivity rate for the virus has declined since 2022. The department also has preliminary evidence that wild birds in some populations have produced antibodies that may offer some protection from the disease and prevent deaths, the spokesperson said.

Himsworth explained there’s a relationship between a host and virus “where they eventually get to an equilibrium where it’s continuing to be transmitted but it’s not as lethal.” 

The extent to which wild birds have been able to develop population-level immunity is still under investigation, the Environment Canada spokesperson said.

While wildlife are generally fairly resilient to a variety of threats, avian influenza can present a different degree of risk for populations already vulnerable for reasons such as extensive habitat loss.

“We are seeing mortality in species at risk across the country, which is concerning,” Joly said. He noted, for instance, that some barn owls — listed as threatened with extinction in western Canada and endangered in eastern Canada — have died from the virus.

Why is bird flu taking such a toll on poultry?

Avian flu is constantly circulating in wild bird populations, which can give wild flocks a chance to adapt and develop a degree of immunity, but domestic bird populations are immunologically  “naive,” Himsworth said. 

Infected chickens and turkeys become sick almost immediately because they are so susceptible to the virus, she said.

Since 2022, more than 12.5 million birds have been culled or died from the virus at more than 480 farms in Canada, according to the Canadian Food Inspection Agency.

“It’s thought that this virus is just so infectious and so lethal that just tiny biosecurity breakdowns like walking it in on the sole of your shoe might be enough to introduce it into the birds,” Himsworth said. “And then once it gets into one bird they’re so susceptible and kept in such high densities that it spreads really quickly through the flock.”

Researchers are investigating whether the virus could be getting into farms through the air or water, Himsworth said. “Because oftentimes you have cases in poultry where there’s no obvious connection to another farm or the biosecurity seems exemplary, but they still get infected.” 

Delta South MLA Ian Paton, the BC Conservatives’ agriculture critic, took to social media to raise concerns about the emotional and financial toll the virus is having on poultry farmers in the province.

“I need this NDP government to step up. Pay attention to these devastated poultry farmers in B.C. and give them the support they need,” he said.

In a statement to The Narwhal, Agriculture and Food Minister Lana Popham said, “Avian influenza outbreaks are incredibly difficult and take a heavy emotional toll on B.C. poultry producers who have spent so much time and care looking after their birds.”

“Though B.C. poultry farmers are incredibly resilient, and I have seen firsthand how they come together to support each other during these challenging times, I have also heard they need to receive compensation from the federal government for their losses sooner, and I’m reaching out to my counterparts in Ottawa to encourage them to make that happen,” Popham said.

A spokesperson for the Agriculture Ministry noted the province launched a $5-million program in 2023 to help B.C. egg and poultry producers prepare and respond to avian flu outbreaks. B.C. also has a program called AgriStability to help farmers facing unforeseen economic losses due to disease outbreaks, the spokesperson said.

Corrected on Dec. 3, 2024 at 6:44 am: This story has been updated to correct the spelling of Damien Joly’s name.