FDA study shows pasteurization kills bird flu in milk

As bird flu continues to spread among U.S. dairy cows, reassuring new government research finds the pasteurization process widely used in the industry effectively kills all bird flu virus in milk.

In a health update posted Friday, the U.S. Food and Drug Administration (FDA) said the results are the latest to show that pasteurized grocery store milk remains safe from the highly pathogenic avian virus H5N1.

"These results complement the FDA's retail sampling study, in which all 297 samples of dairy products collected at retail locations were found to be negative for viable H5N1 HPAI virus," the agency said in its update. "Collectively, these studies provide strong assurances that the commercial milk supply is safe."

The most recent research came about because scientists at the FDA and the U.S. Department of Agriculture (USDA) were trying to replicate the exact conditions under which milk is pasteurized in this country.

"We had a lot of anecdotal evidence. But we wanted to have direct evidence about HPAI [H5N1] and bovine milk," Dr. Don Prater, acting director of the FDA's Center for Food Safety and Applied Nutrition, told CBS News. "So, we began to build this custom instrument that replicates, on a pilot scale, commercial processing [of milk]."

Earlier research had not been quite as convincing: Scientists at the National Institutes of Health (NIH) found that some bits of infectious bird flu virus were able to survive pasteurization in lab tests.

But the FDA said the industry tests showed the so-called flash pasteurization process, which heats milk for at least 15 seconds at 161 degrees Fahrenheit, was killing the virus even before it reached the final stages when milk is held at the highest temperature, offering a "large margin of safety."

"What we found in this study actually is that the virus is completely inactivated even before it gets into the holding tube," Prater noted.

So far, bird flu virus has spread from infected cows to other animals and to three dairy workers through droplets of raw milk teeming with the virus, government officials have said.

Eric Deeble, acting senior adviser for USDA's H5N1 response, said last week that none of the confirmed infected herds so far had been supplying raw milk, CBS News reported.

Prater said a second round of testing will also look at cheese made from raw milk.

The latest results have been submitted to the Journal of Food Protection for peer review and publication, the FDA said.

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