USDA says it’s confident that your hamburger is safe to eat, announcing results of tests showing that cooking patties to an internal temperature of 145 or 160 degrees – medium and well-done – killed the H5N1 virus.

USDA Senior Adviser Eric Deeble said on a call with reporters Thursday that USDA researchers “inoculated ground beef patties at a very high concentration of H5N1 virus surrogate” and then cooked them at different temperatures

Medium and well-done burgers had no virus, but Deeble said after cooking at 120 degrees, “there was virus still in the cooked hamburger patty, although at much, much reduced levels.”

“Just to reinforce the point, these are all experimentally infected burgers,” he continued. “We are doing this in the interest of determining the effectiveness of cooking on killing the virus. But we have not found any of the samples taken at slaughter or from retail meat packaging to have any virus present.”

"I don't think that anybody needs to change any of the safe meat handling or safe cooking practices that are already recommended," Deeble said when asked whether consumers should cook their patties a little longer. He said the Food Safety and Inspection Service long has recommended cooking ground beef to an internal temperature of 160 degrees.

Deeble said USDA is testing beef muscle samples from culled dairy cows and will share those results as soon as they are available.

USDA officials also discussed the latest results from H5N1 testing that have been conducted since a federal order went into effect April 29 requiring testing of lactating dairy cows moving interstate. USDA is requiring testing of a representative sample of the animals they plan to move.  

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The number of affected herds jumped from 36 to 49 between May 7 and May 14, but those herds are located in some of the same states where H5N1 has already been found. Of the 13 herds identified since May 7, eight are in Michigan, three in Idaho, and one each in Colorado and Texas. The other five states where affected herds have been reported are New Mexico, North Carolina, Ohio, Kansas and South Dakota. 

If just one animal tests positive in a herd, USDA considers that herd to be affected.

Affected herds were last reported for Kansas and New Mexico on April 17, in North Carolina and South Dakota on April 9, and in Ohio on April 2.

USDA’s chief veterinarian, Rosemary Sifford, reiterated that the evidence USDA has so far shows that the “spillover event” – where wild birds infected dairy cows – likely occurred in late 2023 in the Texas panhandle, and the virus has spread through movement of those herds, including not just the animals but “the movement of equipment or other items.” 

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