Infectivity and persistence of influenza viruses in raw milk

Influenza A viruses present a significant public health risk, 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 PR8 (IAV PR8) in raw cow milk at 4 °C. We found that IAV PR8 remained infectious in raw milk for up to 5 days, with a decay rate constant of −2.05 day −1 . In contrast, viral RNA remained detectable and stable for at least 57 days, with no significant degradation. Pasteurization (63°C for 30 minutes) significantly reduced detectable viral RNA concentrations, but reduction was less than 1 log. 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 environmental surveillance for influenza viruses. Synopsis Influenza A RNA is persistent in milk, even after pasteurization, and it remains infectious for 5 days in refrigerated milk.