The arrival of Donald Trump in the White House and the installation of the next American administration on January 20, 2025, are fueling all kinds of speculation, questions and fears. Much of this concerns the direction that the 47th US president will take in his country's economy and foreign policy – a direction that will have a profound impact on the lives of hundreds of millions of people. One major issue is missing from the list of concerns, however: the management of the rampant crisis caused by the H5N1 virus, which is circulating intensively in American cattle farms and is a strong candidate to be the source of the next pandemic.
H5N1 has been circulating worldwide for many years, in a variety of variants. The ecology of these avian viruses is well known, at least in part. They circulate quietly in wild bird populations, invading poultry farms through accidental contamination, where the large size of the farms and the low genetic diversity of the animals act as amplification chambers. Tthe viral load in the environment increases, as do the infectivity and pathogenicity of the viruses, and wildlife becomes reinfected through contact with domestic animals, and their movements contribute to the distribution of the pathogen across all continents.
In recent years, the circulation of H5N1 has been spectacular. A wide variety of wild birds have been affected, with sometimes catastrophic consequences for certain endangered species. Cats, foxes, otters, seals, sea lions, lynxes and pumas have also borne the brunt of the virus.
A single genetic mutation
What's new? This time, the virus is American. "Since March 2024, the emergence of clade 2.3.4.4b of the highly pathogenic avian influenza virus H5N1 in non-carnivorous mammals, with infections of goats and dairy cows (...) in several US states, constitutes an epidemiological shift," wrote some 30 experts in the December issue of The Lancet Infectious Diseases. The progress is rapid. The latest report on the situation, under the byline of my colleague Delphine Roucaute, dates back only to December 3 and reported 474 herds having been infected in California, the hardest-hit state.
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