Detection and characterization of highly pathogenic avian influenza A (H5N1) clade 2.3.4.4b virus circulating in Argentina in 2023.

In 2021, avian influenza A (H5N1) clade 2.3.4.4b virus spread to North America and then to Central and South America in October 2022, extending from Colombia to Chile in three months. During 2023, several countries, mostly in the Americas, reported outbreaks in poultry, wild birds and mammals, as well as the emergence of two cases in humans (one in Ecuador in January and one in Chile in March). As of September 20th, 2023, 17 countries in the Americas Region have recorded cases of A (H5N1) in birds and mammals. On February 14th, 2023, Argentina confirmed the first case of avian influenza in wild birds, which was later detected in backyard and commercial poultry, and in the South-American sea lion (Otaria flavescens) in Tierra del Fuego, in the south of the country. So far, 21 suspected cases have been recorded in humans; however, all of them tested negative for Influenza A virus. Hemagglutinin sequence data of animal viruses analyzed in this report showed that Argentinian viruses clustered together with those isolated in other countries of the region. Epidemiological data suggested the possibility of multiple simultaneous entries of the avian virus, highlighting the role of migratory avian populations in the introduction and dissemination of the disease in Argentina. Continued comprehensive surveillance of these viruses in animals and people worldwide, along with ongoing preparedness efforts, are critical to determine the public health risk.