Avian flu virus | Contagious in poultry, benign in humans

Since the discovery of a first breeding contaminated by avian influenza on April 12 in Quebec, six others have been added. The situation is worse elsewhere in Canada, where more than sixty outbreaks have been identified. Update on the current epizootic.

Judith Lachapelle
The Press

Where does this new strain of bird flu come from?

The warmer weather brings with it migratory birds who sometimes land with a few surprises in their luggage… “Birds often carry a set of virus strains,” says Dr.^r Jasmin Villeneuve, medical advisor at the National Institute of Public Health of Quebec (INSPQ). “Among those that mainly attack humans, there are the H1 and H3 strains, which usually circulate in winter. The H5N1 virus is in another category. Extremely contagious in poultry, some variants can kill 80% of the animals on a farm. It can also infect humans. Between 1996 and 2015, about half of the people who caught the H5N1 variant then circulating in Asia died from it. “The variant of H5N1 that we currently have in North America is the one that has been present in Europe since the fall of 2020. It is a little different from the one that we saw in Asia and which circulated before 2015”, says the D^r Villeneuve. In bird flu jargon, unlike COVID-19, variants are called “clades” and have numbers rather than Greek letter names. The H5N1 virus currently circulating is thus the “clade 2.3.4.4b”. “And the analyzes showed that this variant, quite different from the one we saw in Asia, causes infections in birds, but seems to cause fewer infections in humans. »

How is bird flu transmitted to humans?

The cases of human infection of avian influenza that have been reported in connection with the strain that is currently circulating concern people who have been in contact with birds. The first case was reported in Britain last December in a 79-year-old pensioner who raised ducks. At the end of April, US health authorities announced the first case of infection in a Colorado slaughterhouse worker. The infected person, whose only symptom of illness was fatigue, is already cured after being treated with an antiviral drug. “The rate of infection is very low, but we are monitoring it”, says the D^r Villeneuve. “As with COVID-19, when a mutation appears and it becomes more infectious, we want to see it come before it spreads. Influenza vaccines have been developed, but none specifically address the variants currently circulating. “As there are very, very few cases in humans, I don’t think the authorities’ priority is to develop a vaccine for that. To protect yourself from the virus, experts recommend paying attention to disinfection when in direct contact with dead or alive birds. For the consumer of poultry or eggs, no worries: contaminated farm products are destroyed, and if the chicken has to be cooked well, it is because there is more to fear the salmonella bacterium than the virus of influenza.

A price increase to be expected?

If there is less poultry on the market due to the epizootic, should we expect an increase in the prices of eggs and chicken? Not necessarily. “The potential dangers related to epizootics can influence prices,” explains Bruno Larue, professor in the agro-food economics department at Université Laval. In 2014, an epidemic of diarrhea in American piggeries had propelled a rise in pork meat also in Canada – the price of pork in Quebec is adjusted to that of the United States. “Prices fell when the American authorities realized that the problem was not as serious as anticipated,” recalls Mr. Larue. In this case, the price of eggs in the United States could indeed be affected by the risks associated with avian influenza. But egg and poultry production, unlike pork production, is under supply management in Canada. “Prices are set according to production costs. In this case, it is the cost of food that drives prices up. To find out if the price of eggs is increasing at the grocery store, it is therefore better to look at what the hens are eating… “As the price of cereals has risen sharply in recent weeks (corn, wheat in particular), the price of eggs. »

Vaccinating chickens, a possible solution?

In Canada, chicks are vaccinated against several diseases, including Marek’s disease (caused by a carcinogenic virus). But no vaccine against bird flu is yet approved. “The difficulty, when you develop a vaccine in chickens, the costs have to be really minimal, a few cents per dose. Otherwise, it’s not worth it,” says biology professor Denis Archambault, from the University of Quebec in Montreal (UQAM). The latter has precisely worked on the development of a universal vaccine that would protect poultry against several strains of avian flu. Funding for his work, however, was interrupted before the pandemic, laments the researcher. In France, where health authorities have started testing a vaccine on ducks, it is not expected to be able to inoculate poultry on a large scale before the winter of 2023-2024.