The National Institute of Allergy and Infectious Diseases conducted research on the stability of H5N1 influenza virus in raw milk when exposed to different heat treatments commonly used in the dairy industry. The study found that heat treatment at 63℃ resulted in a significant decrease in infectious virus levels, with standard pasteurization measures eliminating the virus entirely after 30 minutes. However, at 72℃, small amounts of infectious virus were still detectable after 15 seconds of heat treatment in some samples. The authors caution that these findings are based on laboratory experiments and may not directly correlate to large-scale industrial pasteurization processes.
In March 2024, an outbreak of highly pathogenic avian influenza virus HPAI H5N1 was reported among dairy cows in Texas, affecting numerous cattle herds across 12 states. While the virus has not shown evidence of person-to-person transmission, public health officials are closely monitoring the situation as part of pandemic preparedness efforts. Three human infections in farm workers with conjunctivitis have been reported, highlighting the need for continued vigilance and research on the potential spread of the virus through dairy products.
The researchers isolated HPAI H5N1 from a dead mountain lion in Montana and tested its stability in raw milk samples through heat treatments at 63℃ and 72℃. They found that both temperatures caused a decrease in infectious virus levels, with 72℃ eliminating the virus within five seconds in most cases. However, small amounts of infectious virus were still detectable after 15 seconds at 72℃ in some samples, indicating the potential for residual virus in milk under certain conditions. The authors emphasize that further studies replicating real-world pasteurization processes are necessary to fully understand the implications of their findings.
While the FDA maintains that the commercial milk supply in the United States is safe, laboratory studies have shown that small amounts of infectious H5N1 virus can survive pasteurization under certain conditions. A survey of retail dairy products found no viable virus in any of the samples, reassuring consumers of the safety of commercially available milk products. However, ongoing pasteurization validation studies are being conducted by the FDA and USDA to further assess the effectiveness of pasteurization methods in eliminating potential viral contaminants. Results from these studies will provide valuable insights into the safety of the milk supply and inform future public health measures.
The findings of the NIAID study highlight the importance of continued research on the stability of H5N1 influenza virus in raw milk and the effectiveness of pasteurization methods in eliminating infectious contaminants. While laboratory experiments provide valuable insights, further studies under real-world conditions are needed to validate these findings and ensure the safety of the milk supply. Public health officials are closely monitoring the situation and taking proactive measures to prevent the spread of avian influenza through dairy products, emphasizing the importance of robust monitoring and surveillance systems to protect public health.
