influenza viruses in raw milk decreased quickly when subjected to heat treatment in a laboratory study. However, even after being treated at 72 degrees Celsius (161.6 degrees Fahrenheit) for 15 seconds, small amounts of infectious virus were still present in raw milk samples with high virus levels. This temperature and duration are commonly used in the dairy industry as a standard pasteurization method. The researchers emphasize that their findings are based on experimental conditions in a laboratory and may not directly apply to large-scale industrial pasteurization processes for raw milk.
The amount of infectious H5N1 rnrnIn a study conducted by scientists at the National Institute of Allergy and Infectious Diseases (NIAID), it was found that heat treatment can significantly reduce the presence of influenza viruses in raw milk. However, even after being treated at 72 degrees Celsius for 15 seconds, some infectious virus was still detectable in raw milk samples with high virus levels. The authors of the study note that these findings are based on laboratory conditions and may not directly apply to industrial-scale processes used by the dairy industry.In a recent study published today in the New England Journal of Medicine, researchers examined the pasteurization processes for raw milk. The study aimed to assess the effectiveness of pasteurization in preventing the spread of harmful pathogens in dairy products.
In late March 2024, there was an outbreak of highly pathogenic avian influenza virus, known as HPAI H5N1, among dairy cows in Texas. This outbreak has affected 95 cattle herds across 12 states, with three cases of human infections detected in farm workers with conjunctivitis. While the virus has not shown any genetic evidence of being able to spread from person to person, public health officials are closely monitoring the situation as part of broader efforts to ensure public safety.The effectiveness of pasteurization in eliminating avian influenza viruses in raw milk is not well understood, so researchers at NIAID’s Rocky Mountain Laboratories conducted a study to determine how H5N1 virus behaves when exposed to the temperatures commonly used in commercial dairy pasteurization. The study involved testing the stability of H5N1 virus in raw milk at 63℃ (145.4 degrees Fahrenheit) and 72℃. The virus was isolated from a dead mountain lion in Montana, and then mixed with unpasteurized cow milk samples. The milk was then heat-treated at different time intervals at the specified temperatures to assess the virus’s resistance to pasteurization.of live virus to survive under certain conditions,” the researchers wrote. “In practice, the vast majority of commercial pasteurization processes will eliminate H5N1 virus, which is highly encouraging, but it is important to recognize that it may not be possible to completely eliminate all infectious virus in all situations. Therefore, ongoing research regarding the effects of temperature and time on viral survival is critical.”
The results of this study provide valuable information for the food industry and public health officials in developing strategies to prevent the spread of H5N1 virus through contaminated food products. By understanding the temperature and time requirements for pasteurization, manufacturers can ensure the safety of their products and consumers can be confident in the safety of the food they consume.The researchers found that the H5N1 virus can still remain infectious in milk even after being heated to 72°C for 15 seconds, as long as the initial virus levels were high enough. They emphasize that their findings are based on experimental conditions and should be further studied using commercial pasteurization equipment, and should not be used to determine the safety of milk in the U.S. Another limitation of their study was that they used raw milk samples with added H5N1 virus, which may differ from milk from cows infected with H5N1 influenza or contain cell-associated virus.Heat effects may have an impact. The authors’ conclusion is that although gastrointestinal infections with HPAI H5N1 virus have occurred in several mammal species, it is still unclear whether consuming live H5N1 in raw milk could make people sick.
As of now, the U.S. Food and Drug Administration maintains that the overall evidence continues to suggest that the commercial milk supply is safe. While laboratory benchtop studies offer valuable information, there are limitations that make it difficult to draw conclusions about real-world commercial processing and pasteurization. The FDA conducted an initial survey of 297 retail dairy products collected.The FDA tested samples from retail locations in 17 states and from 132 processing locations in 38 states, and found that all were negative for viable virus. These results highlight the need for further studies that mimic real-world conditions. The FDA and USDA are working together on pasteurization validation studies, which include the use of a homogenizer and continuous flow pasteurizer. More results will be released as they become available.
