By Deena Beasley and Leah Douglas(Reuters) – Farm workers who have been exposed to animals with bird flu should be tested for the virus even if they do not have symptoms, the U.S. Centers for Disease Control and Prevention said on Thursday.The change to the agency’s testing recommendation comes as the U.S. Department of Agriculture is also expanding its testing of milk for bird flu, signaling concern by both agencies about the ongoing spread of the virus on dairy and poultry farms.Bird flu has infected nearly 450 dairy farms in 15 states since March, according to USDA data.The CDC is not seeing mutations in the virus that would lead to easier transmission or evidence of person-to-person spread, agency officials said on a press call.The CDC has identified 46 human cases of bird flu since April, though farm worker groups have suggested the figure is an undercount as workers avoid testing for fear of economic repercussions from quarantining or because their symptoms are too mild to warrant concern.Disease experts have warned that as the virus circulates, the risk of it more easily infecting humans increases, which could lead to a pandemic.”There may be individuals who were infected with H5 but who do not recall having symptoms. That means that we in …