Beef tissue from a sick cow tests positive for avian influenza virus

The USDA said the fact that inspectors identified the diseased cow and prevented its meat from entering the food chain was proof that its protocols were working. But some infected cows are asymptomatic and may not be detected by such inspection systems. The agency found no viruses in ground beef samples collected from outlets in states where the cows tested positive.

So far, the agency’s Food Safety and Inspection Service has tested tissue samples from 96 dairy cows that had been condemned for signs of disease. Only samples from one cow tested positive for the H5N1 virus, according to the agency, which is analyzing additional muscle samples.

The findings released Friday are further indication that people should be careful when cooking and preparing meat, said Dr. David Acheson, former medical director of the Food Safety and Inspection Service at the USDA. Food safety experts always recommend cooking meat thoroughly to prevent infection from common pathogens such as salmonella, listeria and E. coli.

“These food safety recommendations were in store long before H5N1 became a problem, and they should always be our baseline standard,” said Dr. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory at the University of Wisconsin -Madison.

Earlier this month, the USDA released the results of an experimental study in which researchers added high concentrations of the virus to beef patties. The researchers found no viruses present in the meat when they cooked the hamburger to 160 degrees Fahrenheit, the internal temperature of a well-done hamburger, or 145 degrees Fahrenheit, the temperature of a hamburger cooked to medium.