FDA: Bird flu viral fragments in milk were dead; pasteurization works

Although fragments of the H5N1 bird flu virus were found in one-fifth of milk purchased in grocery stores, a new round of high-precision testing “did not detect any live, infectious virus” and reaffirmed that the commercial milk supply is safe, said the FDA.

Meanwhile, bird flu was found in a dairy herd in Colorado, the ninth state since the disease was identified for the first time in cattle a month ago.

A federal order took effect on Monday that requires dairy farmers to have lactating cows tested for the H5N1 virus before they are shipped across state lines. The Agriculture Department said on Saturday that the tests are not needed if cows are sent to an auction barn for sale to a slaughterhouse. “We are announcing this clarification over the weekend to ensure small farms have the guidance necessary to continue to move cull cattle and limit animal welfare issues,” said the USDA.

The Food and Drug Administration said there has been no uptick of human cases of the flu or no cases of H5N1 bird flu in people beyond the dairy worker in Texas who contracted the highly pathogenic avian influenza (HPAI) from direct contact with infected cattle, citing “epidemiological signals” tracked by the CDC.

In an update, the FDA said “preliminary results of egg inoculation tests on quantitative polymerase chain reaction (qPCR)-positive retail milk samples show that pasteurization is effective in inactivating HPAI.” The agency described the egg inoculation tests as the gold standard for determining if infectious virus is present. The tests were performed on a limited set of geographically targeted samples collected as part of a national milk-sampling study.

“This additional testing did not detect any live, infectious virus. These results reaffirm our assessment that the commercial milk supply is safe,” said the FDA on Friday.

Several samples of infant formula and powdered milk products marketed as toddler formula were subjected to qPCR tests. “All qPCR tests were negative, indicating no detection of viral fragments or virus in powdered formula products,” said the agency.

In addition, the FDA said it was in the process of further assessing samples from its study of 297 samples of retail dairy products purchased in 38 states. All samples that tested positive for the H5N1 virus during PCT tests were going through egg inoculation tests. A day earlier, the agency said initial results showed about one in five of the samples contained viral fragments, based on qPCR testing, “with a greater proportion coming from milk in areas with infected herds.”

To date, the H5N1 bird flu virus has been confirmed in 34 herds in nine states, from Idaho to North Carolina. Texas has the most infected herds, 12.

The CDC said the risk to the public from bird flu viruses was low.

The USDA said it would bear the cost of testing dairy cattle for the virus. That includes samples from cattle showing symptoms of bird flu, samples from “other animals on dairy farms associated with this disease event,” and samples submitted by producers who want to know the disease status of cattle not displaying signs of bird flu, along with the mandatory tests for livestock awaiting shipment to another state.

Testing is intended to prevent the spread of the H5N1 virus and to help researchers learn more about how it spreads, said the USDA. The virus has moved from cow to cow, cow to poultry, and herd to herd. Some outbreaks are believed to stem from the introduction of infected cows into previously uninfected herds.

In a risk assessment, the World Health Organization, the Food and Agriculture Organization, and the World Organization for Animal Health (WOAH), recommended in view of the spread and evolution of bird flu viruses, countries be alert for the possibility of human infections.

“Countries should maintain surveillance in birds, monitor and investigate cases in non-avian species, including livestock, report cases of HPAI in all animal species to WOAH and other international organizations, prevent spread in animals through strict biosecurity measures and protect persons in contact with suspected/infected animals,” said the organizations.