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A rare avian influenza strain, H5N9, has been identified in a U.S. duck farm, marking its first appearance in commercial poultry since 2013. This new variant, linked to a November outbreak in California’s Merced County, shows promise of causing severe disease in birds, humans, and other animals due to a genetic recombination event that combined elements from H5N9 and the previously dominant H5N1 strain.
Ducks are highly susceptible to harboring low-pathogenicity influenza viruses without exhibiting clinical symptoms, making them key mixing vessels for bird flu. The discovery suggests potential risks of rapid spread among wild populations or human communities if transmission occurs outside controlled environments. While no evidence of human-to-human transmission has been found in the U.S., ongoing efforts to cull 3 million birds at Merced County farms highlight the gravity of the threat.
H5N9’s unique genetic makeup, including mutations conducive to human susceptibility, could outcompete H5N1 and expand its reach. Scientists emphasize that past outbreaks of similar strains have faced limited success in establishing significant public health risks, but this new variant represents a notable shift in potential impact.
Source: https://www.cbsnews.com/news/h5n9-h5n1-bird-flu-what-to-know