Europe faces “the biggest epidemic observed to date”

This is “the epidemic [de grippe aviaire] the largest observed to date in Europe ». In a report published Monday, October 3, the European Food Safety Authority (EFSA) confirms that the 2021-2022 season was exceptional in several respects. In the period from June to September, EFSA reports a “Unprecedented number of highly pathogenic avian influenza virus detections in wild and domestic birds”. The summer was particularly marked by a “unusual persistence of virus in wild birds” observed in fifteen European countries. Fatal outbreaks have been observed in seabird breeding colonies (gulls, gulls, gannets, etc.) on European coasts, particularly in France, the Netherlands and the United Kingdom.

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However, the summer period is normally the calm period for the circulation of the avian influenza virus, which traditionally spreads during the migration phases of wild birds from north to south. A consequence of this interrupted seasonality and the persistence of the virus among the sedentary fauna: farms were not spared during the summer, when they already experienced a particularly virulent epidemic in the first half of 2022. In total, 47 million birds had to be slaughtered in Europe this year, including 16 million in France. After a dismal winter and spring, the period from June to September saw “The number of epidemic outbreaks in poultry has decreased compared to previous months, but was more than five times higher compared to the same period of the previous year”continues the EASA.

Monitored mammalian transmissions

Another notable fact, according to the European agency: “The geographic scope of this year’s outbreak is unprecedented, with reported cases ranging from the Svalbard Islands in Norway to southern Portugal and the far east of Ukraine, affecting a total of thirty-seven countries across the continent. European. » This same H5N1 virus also crossed the Atlantic in the fall of 2021 and caused an unprecedented level of contamination in North America. In France, the areas so far relatively spared are at the forefront this year, particularly Brittany, with a high risk of dispersion between farms, due to its high density.

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Finally, the particularity of this year’s epidemic is that it is dominated by a subgroup of H5N1 viruses, clade 2.3.4.4b, first identified in the Netherlands in October 2020. Since these viruses are very prone to rearrangement, several genotypes are circulating, some of which have appeared very recently since June. The adaptive capabilities of these viruses are thus one of the explanations for their persistence during the summer. Health authorities are particularly monitoring transmissions to mammals, the virus has been detected this year in many species (foxes, badgers, weasels, lynx, porpoises, otters, seals, dolphins, grizzly bears, etc.). However, no diffusion between mammals was observed. As for the risk of transmission to humans, it is considered low in the general population by EFSA, and low to medium for people who work professionally on farms.

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