Avian Influenza A(H5N1) virus in Cow's Milk: Heat inactivation and mouse infectivity
A correspondence published in The New England Journal of Medicine discusses the detection of highly pathogenic avian influenza virus (HPAI) of the H5N1 subtype in cow's milk, raising concerns about its potential impact on the human food chain. The study demonstrated that untreated milk containing HPAI A(H5N1) virus can infect susceptible animals that consume it. In the trial involving mice, researchers orally inoculated the mice with HPAI A(H5N1)-positive milk. The mice showed signs of illness starting on day 1, and high virus titers were detected in the respiratory organs, suggesting that infection may have occurred through the pharynx. Moderate virus titers were found in several other organs, consistent with the systemic infections typically caused by HPAI H5 viruses in mammals. Additionally, virus detection in the mammary glands of two mice indicated a high virus load in the milk of lactating cows, even though the mice themselves were not lactating.
These findings highlight the potential risks associated with the consumption of untreated milk contaminated with the HPAI A(H5N1) virus. Furthermore, heat treatment at 72°C for 15 or 20 seconds reduced virus titers by more than 4.5 log units but did not completely inactivate the virus. While the laboratory conditions used in the study reduced virus titers significantly, the researchers emphasized that these conditions may not fully replicate large-scale industrial pasteurization processes.
