This is “epidemic [de grippe aviaire] the largest observed in Europe so far ». In a report published on Monday 3 October, 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 detections of highly pathogenic avian influenza virus in wild and domestic birds”. The summer was especially marked by a “unusual persistence of virus in wild birds” observed in fifteen European countries. Fatal outbreaks have been observed among nesting colonies of seabirds (gulls, gulls, terns, etc.) on European coasts, particularly in France, the Netherlands and the United Kingdom.
However, the summer season is usually a quiet period for the circulation of the bird flu virus, which is traditionally spread during the migration phases of wild birds from north to south. The consequence of this disturbed seasonality and the persistence of the virus among sedentary fauna: farms were not spared even in the summer, when they already experienced a particularly virulent epidemic in the first half of 2022. In total, 47 million poultry had to be slaughtered in Europe this year, including 16 million in France. After the dark winter and spring came the period of June-September “The number of outbreaks in domestic birds decreased compared to previous months, but was more than five times higher compared to the same period last year”EFSA continues.
Mammal transmissions monitored
Another noteworthy fact according to the European agency: “The geographic scope of this year’s epidemic is unprecedented, with reported cases ranging from the Svalbard Islands, Norway, southern Portugal to Ukraine, affecting a total of thirty-seven countries on the European continent.” » The same H5N1 virus also crossed the Atlantic in the fall of 2021 and caused unprecedented levels of contamination in North America. In France, relatively spared areas, especially Brittany, are on the front line this year, with a high risk of spreading between farms due to their high density.
Finally, the epidemic is peculiar this year in that it is dominated by a subgroup of H5N1 viruses, clade 188.8.131.52b, first identified in the Netherlands in October 2020. These viruses greatly facilitate reassortment, several genotypes are circulating, some of which have only recently appeared since June . The adaptability of these viruses is thus one of the explanations for their persistence during the summer. Health authorities are particularly monitoring transmission to mammals, the virus was detected in many species this year (foxes, badgers, polecats, lynxes, porpoises, otters, seals, dolphins, brown bears, etc.). However, no diffusion between mammals was observed. The risk of transmission to humans is considered low in the general population and low to moderate in people working professionally on farms, according to EFSA.
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