In raw milk samples spiked with high amounts of , small amounts of infectious virus were still detectable after treatment with a standard pasteurization method, researchers said on Friday. The findings reflect experimental conditions in a laboratory and should not be used to draw any conclusions about the safety of the , according to the authors of the study from the US government's National Institute of Allergy and Infectious Diseases (NIAID) Rocky Mountain Laboratories. The research was published in the Compared to the spiked raw milk floating freely used in the study, raw milk from cows infected with H5N1 influenza may have a different composition or contain virus inside of cells, which may impact heat effects, the researchers said.
US dairy cows were found to be infected with bird flu in March. The US Food and Drug Administration surveyed pasteurized retail samples of milk and estimated that a fifth of the US milk supply contained strands of virus. The agency has said that pasteurized milk is safe to drink.
The virus used in the experiments had been isolated from the lungs of a dead mountain lion, mixed with raw, unpasteurized cow milk samples, and heat-treated at 63 degrees C (145.4 degrees F)and 72 degrees C (161.6 degrees F) for different periods of time.
After treatment at 72 degrees C for 20 seconds – five seconds longer than the industry standard for pasteurization at that temperature - very small amounts of infectious virus were detected in one of three samples, .
