Infectious H5N1 influenza virus in raw milk rapidly declines with heat treatment

The amount of infectious H5N1 influenza viruses in raw milk rapidly declined with heat treatment in laboratory research

The amount of infectious H5N1 influenza viruses in raw milk rapidly declined with heat treatment in laboratory research conducted by scientists at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. However, small, detectable amounts of infectious virus remained in raw milk samples with high virus levels when treated at 72 degrees Celsius (161.6 degrees Fahrenheit) for 15 seconds — one of the standard pasteurization methods used by the dairy industry. The authors of the study stress, however, that their findings reflect experimental conditions in a laboratory setting and are not identical to large-scale industrial pasteurization processes for raw milk. The findings were published today in the New England Journal of Medicine

In late March 2024, United States officials reported an outbreak of highly pathogenic avian influenza virus called HPAI H5N1 among dairy cows in Texas. To date, 95 cattle herds across 12 states have been affected, with three human infections detected in farm workers with conjunctivitis. Although the virus so far has shown no genetic evidence of acquiring the ability to spread from person to person, public health officials are closely monitoring the dairy cow situation as part of overarching pandemic preparedness efforts.

Given the limited data on the susceptibility of avian influenza viruses to pasteurization methods used by the dairy industry, scientists at NIAID’s Rocky Mountain Laboratories sought to quantify the stability of H5N1 virus in raw milk when tested at different time intervals at 63℃ (145.4 degrees Fahrenheit) and 72℃, the temperatures most common in commercial dairy pasteurization processes. The scientists isolated HPAI H5N1 from the lungs of a dead mountain lion in Montana. Then they mixed these viral isolates with raw, unpasteurized cow milk samples and heat-treated the milk at 63℃ and 72℃ for different periods of time. The samples were then cell-cultured and tested to determine if live virus remained and if so, how much.

fresh natural milk on a farm

Fresh natural milk on a farm. Given the 2024 multistate outbreak of H5N1 influenza among U.S. dairy cows, federal authorities recommend against drinking unpasteurized (raw) milk.

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This page was last updated on Friday, June 14, 2024