Avian Influenza A(H5N1) Emergence Unit

Status: active - level 1

Last updated on 22 July 2024

The essential

In April 2024, the first transmission of avian influenza A(H5N1) virus from a mammal to humans was observed in the United States. Three dairy farm workers developed ocular and respiratory symptoms without serious complications, following direct exposure to cows carrying the virus. Infection with this virus is exceptional in cattle, and until now, reported human cases of avian influenza A(H5N1) infection worldwide have been limited to close contact with infected birds.

The route by which the avian influenza virus is introduced into cattle remains uncertain, potentially linked to the consumption by dairy cows of bedding soiled by infected bird droppings.

These sporadic human infections are accompanied by infections in new species of wild and domestic mammals that were previously spared. This follows a continuous circulation of the virus in wild bird colonies, leading to an unprecedented increase in the number of outbreaks in poultry farms in many countries in Africa, Asia, Europe and North America.

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As part of ANRS MIE’s Emergence program, the agency provides a weekly scientific watch on avian influenza A(H5N1) to keep abreast of research progress.

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