The FDA announced Monday it has begun collecting samples of aged raw cow's milk cheese to test for bird flu as the U.S. battles an outbreak of the virus.

The FDA has begun testing cheese for bird flu as human cases of the virus continue to rise in the United States.

Raw, unpasteurized milk is a known vector of bird flu when derived from infected cow herds. It can also contain pathogens such as E. coli, salmonella, and both Streptococcus and Staphylococcus bacteria.