Is bird flu about to be transmitted from human to human? According to research published in the journal Science Thursday, December 5, the current version of the H5N1 flu virus is just one mutation away from spreading more easily among humans.
American researchers say that several elements suggest that avian flu could trigger a new pandemic, including the recent genetic sequencing of a Canadian teenager sick with the flu. This showed that the virus had begun to evolve to find ways to bind more easily to the body’s cells – which would be worrying, according to the researchers, in the absence of acquired immunity in humans. Nearly half of the 904 human cases of H5N1 recorded since 2003 have been fatal, according to the World Health Organization.
Contaminated dairy cows
Experts also explain that the virus can spread more quickly and easily by mutating, by circulating in different animals and species. But that is the case. “We were surprised by this avian flu epidemic since until recently it mainly affected wild and farmed birds in Eurasia, and it has now spread to the American continent among mammals”summarizes Serge Morand, specialist in parasitic ecology.
After spreading very quickly across the entire North American continent, then South America in 2022, even reaching the edge of Antarctica, avian flu experienced a new evolution by contaminating several flocks of American dairy cows in March 2024. “The organization of dairy cattle farms in the United States undoubtedly facilitated this massive contamination, explains Jean-Luc Guérin, professor at the National Veterinary School of Toulouse and unit director at INRAE. In this context, it is a particular genotype which infects dairy cattle and which is also the cause of contamination in humans. The ability of the virus to infect humans is based, among other things, on a few key mutations: you have to imagine a key and lock system: the mutations are small modifications to the key which will make it easier to pass through the lock. and also the entry of the virus into the target cell. In this case, these strains present mutations which make it easier for them to infect mammals and humans. »
If the virus remains fundamentally adapted to the bird, “it is true that observations in the United States reveal that the strain which is circulating has an increased potential for transmission to humanscontinues Jean-Luc Guérin. Human cases in California are particularly closely watched. Ongoing investigations aim to ensure that there is no low-noise circulation in humans. Today, of the fifty human H5N1 cases reported in the United States, two or three have not been able to be linked to a link with the animal, which remains marginal, but these are the cases that must be studied intensively. to understand their origin and, above all, to ensure that they do not multiply”he adds.
Vaccination success
After a first case detected in a child, the World Health Organization has called on the international community to strengthen its surveillance in recent weeks. In France, the level of risk linked to avian flu has been raised by ” moderate “ has ” pupil “ on November 9, the highest level which notably involves the confinement of poultry. The country was affected from 2015 to 2017 and then almost continuously since the end of 2020. Tens of millions of poultry have been euthanized in recent years, causing economic losses amounting to billions of euros.
It is to break this spiral that in the fall of 2023 France made vaccination compulsory in farms with more than 250 ducks. It is the only country in Europe to vaccinate farm animals against avian flu. “The duck vaccination plan seems to protect our farms, which is good news. The situation today remains very mixed on an international scale: there are factors of concern and factors of reassurance. This shows that it is absolutely and more essential than ever that veterinarians and doctors work together. This disease clearly shows that everything is intertwined”summarizes Jean-Luc Guérin.
“The number of domestic animals for breeding continues to increase, regrets Serge Morand for his part. The weight of cows on the planet is greater than that of human beings, and there will soon be more chickens than wild birds. We must work on this production system, otherwise we will continue to see epidemic after epidemic. »
