Infectivity and Persistence of Influenza A Virus in Raw Milk

Influenza A viruses present important public health risks, with recent outbreaks of highly pathogenic avian influenza (HPAI) H5N1 in dairy cattle raising concerns about potential transmission through raw milk consumption. This study investigated the persistence of influenza A virus H1N1 PR8 (IAV PR8) in raw cow milk at 4 °C. We found a first-order decay rate constant of −2.05 day–1 equivalent to a T99 of 2.3 days. Viral RNA remained detectable for at least 57 days with no degradation. Pasteurization (63 °C for 30 min) reduced infectious virus to undetectable levels and reduced viral RNA concentrations, but reduction was less than 1 log10. These findings highlight the potential risk of zoonotic virus transmission through raw milk consumption and underscore the importance of milk pasteurization. The prolonged persistence of viral RNA in both raw and pasteurized milk has implications for food safety assessments and environmental monitoring, particularly in the context of the environmental surveillance of influenza viruses.