Two Cases of Influenza A(H5) Virus Infection Detected in U.S. Dairy Workers
In a recent development, two cases of Influenza A(H5) virus infection have been identified in dairy farm workers in the United States. The first case was reported on April 1, 2024, in a Texas dairy farm worker who tested positive for highly pathogenic avian influenza (HPAI) A(H5N1) virus after exposure to infected dairy cattle. The patient experienced only conjunctivitis and recovered after treatment with oseltamivir. Subsequently, on May 22, 2024, a second case was reported in a Michigan dairy farm worker. Both cases are believed to be the first instances of cow-to-human transmission of an avian influenza A virus.
The outbreak of A(H5N1) virus in U.S. dairy cattle was first reported in March 2024, with infected cows identified in 52 herds across nine states. Signs in the cattle included decreased milk production and clear nasal discharge. Additionally, the virus was found in unpasteurized milk from infected cows.
Internationally, cases of human A(H5N1) infection have been reported since 1997, with 909 cases documented, leading to a 52% fatality rate. To address the current outbreak, the CDC has implemented a One Health approach, including monitoring exposed individuals, conducting surveillance, and researching virus pathogenesis.
In response to the situation, CDC is enhancing influenza surveillance activities, collaborating with manufacturers for diagnostic tests, and developing novel vaccines for pandemic preparedness. Additionally, antiviral drugs such as oseltamivir are recommended for treatment and post-exposure prophylaxis.
Epidemiologic investigations are underway to assess the risk to humans, with plans for in-depth studies and specimen collection. CDC’s efforts aim to better understand and address the spread of Influenza A(H5) virus in the United States.
