Is bird flu becoming dangerous for humans?

Avian flu is not slowing down in the United States. Wednesday, a 61^e Human contamination has been recorded since April, when the H5N1 virus spread to dairy cows in the country. Until now, patients suffered from mild symptoms, notably conjunctivitis. But for the first time, the case turned out to be serious: a patient over 65 years old was hospitalized in Louisiana in critical condition and suffering from a severe respiratory illness. “When this virus positions itself in the lungs, it causes monstrous damage and mortality is very high,” explains Bruno Lina, virologist in Lyon and member of Covars.

Is a potential pandemic possible? The scientist reassures: “This avian virus is not transmitted between humans. As long as this virus maintains this phenotype, this behavior, there is no danger. » “The risk of a pandemic is extremely low for the traditional population and moderate for agricultural workers,” adds Eric Cardinale, scientific director of animal health at Anses. “As long as there is no human-to-human transmission, we are rather reassured. But the increase in cases increases our vigilance. »

A very virulent lineage

The threat of avian flu is not new, with the H5N1 strain of the virus first identified in 1996. But since 2020, the 2.3.4.4B lineage has spread in the United States, with two particularities: very high contagiousness and contamination of around fifty mammals, including dairy cows. “We find ourselves today with a circulation of this virus in wild and farmed fauna which is extremely high and which, above all, is not controlled,” analyzes Bruno Lina. With more and more sick animals, the risks of contamination in humans are increasing, statistically, particularly among agricultural workers.

The high circulation of the avian flu virus among mammals is not trivial. Experts fear that an increase in infections will make it easier for the virus to mutate. At the beginning of November, the case of a young Canadian caused concern: the avian flu virus mutated after infecting him, to the point of presenting characteristics that could make it transmissible between humans. The teenager was placed in isolation in critical condition, but the epidemiological investigation revealed no transmission of the virus to relatives. To have a large-scale chain of contamination, a series of mutations of the virus currently in circulation would be required. “For the moment, we don’t see it at all,” summarizes Bruno Lina.