Laboratory evaluation conducted at the Rocky Mountain laboratory of the National Institute of Allergy and Infectious Diseases determined the temperature and time parameters required to inactivate virus in milk.* Raw milk was spiked with a virulent H5N1 isolated from a mountain lion.  At 145.4F (63C), it was possible to achieve a 10-log reduction in virus after 2.5 minutes.  Applying 161.6F (72C) for 15 seconds a four-log reduction occurred, but infectious virus was present following 20 seconds of heat treatment in one of 3 replicates.  It was determined that 15 seconds at 161.6F was adequate to completely inactivate the virus.

The paper emphasized that the evaluation of time and temperature was carried out under laboratory conditions and that cows infected with H5N1 may produce milk with different characteristics to raw milk from unaffected glands.  It is unknown whether mammals can be infected with H5N1 virus by the oral route.  On the basis of the evaluation, conventional pasteurization at 161.6 degrees should be adequate to inactivate H5N1 virus in milk.

*Kaiser, F. et al. Inactivation Rate of Highly Pathogenic Avian Influenza H5N1 Virus (clade 2.3.4.4b) in Raw Milk at 63 and 72 Degrees Celsius. The New England Journal of Medicine doi:10.1056/NEJMc 2405488 (2024)