Rolfes, M.A., Kniss, K., Kirby, M.K. et al. Human infections with highly pathogenic avian influenza A(H5N1) viruses in the United States from March 2024 to May 2025. Nat Med (2025)
Between March 2024 and October 2024, 46 human cases of highly pathogenic avian influenza (HPAI) A(H5N1) had been detected in the United States. The persistent panzootic spread of HPAI A(H5N1) viruses and continued detection of human cases presents an ongoing threat to public health. Between November 2024 and May 2025, an additional 24 cases have been reported for a total of 70 human cases of HPAI A(H5N1): 41 were exposed to dairy cows, 24 to commercial poultry, 2 to backyard poultry, and 3 had an unidentified source of exposure. All sequenced viruses were clade 2.3.4.4b. Overall, 62 cases (89%) reported eye redness, 32 (46%) fever, and 29 (41%) respiratory symptoms; 54 of 67 cases (81%) reported receiving antiviral treatment. Most illnesses were mild; however, four patients were hospitalized. Of the hospitalized patients, three had pneumonia and one died. No human-to-human transmission was detected. Occupational exposure to infected animals was a risk factor for HPAI A(H5N1) virus infection and the risk to the general population remains low; however, the two cases exposed to infected backyard poultry and three cases with unidentified exposures highlight that ongoing vigilance is warranted.
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