Scientists who took milk with the highly pathogenic avian influenza and pasteurized it found that detectable amounts of the influenza remained after the heat treatment was applied, according to a study published on June 14. The group took H5N1 and diluted it in raw, unpasteurized cow milk. They then heat-treated the milk at 145 degrees Fahrenheit, and 161 degrees Fahrenheit.
Commercial milk must be pasteurized at one of three temperatures: either 145 degrees for 30 minutes, 161 degrees for 15 seconds, or 191 degrees for one second. The testing indicated that the lowest level of pasteurization would be sufficient due to the length of time that level requires, but the scientists found detectable amounts of the virus in milk treated at 161 degrees after 20 seconds of heat treatment. “This finding indicates the potential for a relatively small but detectable quantity of H5N1 virus to remain infectious in milk after 15 seconds at 72°C if the initial virus levels were sufficiently high,” Mr.
Munster and the other authors wrote. The paper was published by the New England Journal of Medicine. Disclosure forms listed employment by two authors by non-NIAID agencies as conflicts of interest.
Limitations included using raw milk samples spiked with the virus, since raw milk from cows infected with H5N1 could have a different makeup. The work, supported by government funding, may not translate to commercial milk because it was conducted in the lab, the researchers stressed. They said .
