All but one case of people infected with highly pathogenic avian influenza (HPAI) A(H5N1) virus in California have occurred in dairy workers who were exposed to sick cows, according to a new CDC report. The first human case of HPAI A(H5N1) virus in California was identified in September 2024. From Sept. 30 through Dec. 24, 2024, 38 people in the state received a positive test for the virus. Of these, 37 were determined to be dairy farm workers who were confirmed to have had contact with infected cows.
The final case occurred in a person younger than 18 years of age who had an undetermined exposure. This case represents the first pediatric case of HPAI A(H5N1) infection identified in the United States. The child had mild respiratory symptoms and otitis media, was prescribed oseltamivir, and recovered quickly.