Ground beef being sold at retail stores in the U.S. is being tested for H5N1 bird flu, part of a wider investigation into an outbreak that’s affecting dairy cows, though officials remain confident that the meat is safe for human consumption. A spokesperson for the U.S. Department of Agriculture (USDA) said it’s currently working on three separate beef safety studies to confirm that usual practices are sufficient to keep the meat supply safe from H5N1 bird flu. “For the first, samples are being collected at retail outlets in the states in which dairy cow herds have tested positive for H5N1 infl…