Is avian flu spreading? What a discovery in Canadian skunks means for outbreak

The Star spoke to influenza experts about H5N1 and if you should be worried.
Thestar.com
March 16, 2023
Kelly Skjerven

In the latest incident of an avian flu outbreak that has been ongoing for the last year and mostly affecting birds, there is now proof the virus has spread to other animals after officials in B.C. announced eight dead skunks tested positive for avian flu.

The Star spoke to influenza experts Matthew Miller, director of the DeGroote Institute for Infectious Disease Research at McMaster University and Shayan Sharif, acting dean for the Ontario Veterinary College and pathobiology professor, about H5N1 and if you should be worried.

What is Avian flu?

Avian flu, or H5N1, is a highly pathogenic virus that is typically found in aquatic birds such as ducks or geese. Miller said what most people don’t know is ducks and geese are the natural hosts of influenza. Humans tend to get infected with the seasonal flu, H1N1 or H3N2.

Miller said there are 18 subtypes of hemagglutinin (the H) and 11 subtypes of neuraminidase (the N). “So humans, as you can imagine, really experience very little of all the diverse flus that are out there.”

Most flus that infect birds are low pathogenic, meaning the birds are infected but they don’t really experience any severe symptoms and don’t usually die.

Miller explained H5N1 is highly pathogenic and causes severe mortality in birds and other animals when spillover occurs -- when a pathogen transmits from its natural host to other species.

In birds, the flu is primarily a gastrointestinal infection, birds spread it through their feces. In humans, the flu is a respiratory infection.

What’s unique about H5N1 is that its mutations and features allow it to cause infection in almost all tissues of the body, including the brain and can cause encephalitis which is difficult to treat, which is why H5N1 is so deadly in animals and humans.

Sharif added that animals start dying usually within 48 to 72 hours of exposure.

Can avian flu spread to humans?

Avian flu can spread to humans and as Miller explained, “the mortality rates tend to be very high when that happens.”

Humans are infected with H5N1 through direct contact.

“Most often when we see human spillovers, it’s poultry workers or in places like southeast Asia and parts of the middle east where people have free range chickens that they keep on the property for a food source,” Miller said.

Miller said in these cases, people can become infected when they butcher the meat and come into contact with the blood and intestinal contents of the bird.

Health Canada states highly pathogenic avian flu is not a food safety concern, with no evidence to suggest that eating cooked poultry or eggs could transmit the virus to people.

Sharif said there have only been a handful of cases of human infection with this particular strain of influenza, but experts are concerned the virus could accumulate genetic mutations.

Since 2003, there have been 868 cases of avian flu in humans reported from 21 countries, according to the World Health Organization. Of those cases, 457 were fatal. In the Western Pacific Region, 240 cases have been reported, including 135 deaths.

Can avian flu spread to other animals?

Avian flu can spread to other animals, like the case in B.C. Animals that are high risk of becoming infected with H5N1 are ones that are in proximity with the infected birds.

“We’ve heard a lot about outbreaks in sea lions, for example. They’re coastal animals so that’s to be expected,” Miller said.

Ducks also roost in farm areas during migration so Miller said it’s also common to see spillover of avian flu into pigs and other livestock.

Both Miller and Sharif said they can’t say for sure how the skunks in B.C. were infected, but because they are scavenger animals it’s likely they ate a dead bird that was infected.

Sharif said this isn’t the first time that skunks have become infected. Other scavenger animals like raccoons, foxes as well as bears have also been infected.

Should we be worried?

Miller said the good news is that at this point, there’s no suggestion the virus spreads efficiently from human to human.

Though it’s not “an imminent pandemic threat,” Miller said its worth closely watching because when H5N1 spreads to humans the death rate can be as high as 50 per cent.

Miller added being in the vicinity of dead animals doesn’t lead to a high risk of catching the virus.

“Breathing the air in the vicinity of a dead animal is not going to give you H5N1 but handling it without appropriate protections increases that risk substantially,” Miller said.

Sharif said one thing that concerns him is the virus has killed close to 4,000 sea lions in a small area in Peru, leading to concerns there may be transmission between the sea lions, versus sporadic transmission, when the animal is infected from a bird.

How can we protect ourselves?

Miller and Sharif said the best thing people can do is avoid direct contact with dead animals.

“If they see dead animals it would be better to call the city or a local wildlife authority to investigate and then dispose of those animals rather than handling (the dead animal) themselves,” Miller said.

Miller added there are some antivirals used to treat high risk people who have seasonal flu, and that it’s likely these could be effective against highly pathogenic avian flu as well.

Sharif said many in the field think using a one health approach is the best way to mitigate the virus spreading -- looking at animals, humans and the environment they live in to get a better understanding of what those in the field can do to ensure they’re doing a better job of surveillance when it comes to all animals, humans and the environment they live in.

Sharif said it’s also important to start thinking about if poultry or humans should be vaccinated, though he doesn’t think we’re at that stage yet.“This is not the time to panic. This is really the time to be ready and be prepared for the possibility, even though there is low likelihood of that consequently, there is a possibility that this virus could be a pandemic potential virus, and we have to be ready for it.”