Highly Pathogenic Avian Influenza A(H5N1) Virus Infections in Humans

This CDC-led study details 46 confirmed U.S. human infections with H5N1 avian influenza between March and October 2024. All but one case occurred in adults with occupational exposure to infected poultry or dairy cows. Most cases presented with mild symptoms, predominantly conjunctivitis (93%), and none required hospitalization. A single case without known animal exposure was detected through routine surveillance. The majority of patients received prompt oseltamivir treatment (87%), typically within two days of symptom onset. Conjunctival swabs were critical for diagnosis, yielding positive results in 90% of patients with conjunctivitis. No evidence of human-to-human transmission was found, even among 97 monitored household contacts. The report emphasizes suboptimal use of personal protective equipment among dairy and poultry workers and calls for enhanced farm-level biosecurity, rapid testing, and continued One Health surveillance. Genetic sequencing showed no markers of increased transmissibility.

This CDC-led study details 46 confirmed U.S. human infections with H5N1 avian influenza between March and October 2024. All but one case occurred in adults with occupational exposure to infected poultry or dairy cows. Most cases presented with mild symptoms, predominantly conjunctivitis (93%), and none required hospitalization. A single case without known animal exposure was detected through routine surveillance. The majority of patients received prompt oseltamivir treatment (87%), typically within two days of symptom onset. Conjunctival swabs were critical for diagnosis, yielding positive results in 90% of patients with conjunctivitis. No evidence of human-to-human transmission was found, even among 97 monitored household contacts. The report emphasizes suboptimal use of personal protective equipment among dairy and poultry workers and calls for enhanced farm-level biosecurity, rapid testing, and continued One Health surveillance. Genetic sequencing showed no markers of increased transmissibility.