Photo: REUTERS/Dado Ruvic/Illustration/File

Explainer: How U.S. states are testing for bird flu

Reading Time: 2 minutes States in the U.S. are playing a key role in the nation's response to a growing outbreak of avian flu among dairy cattle that has also infected a small number of humans. The states are chiefly responsible for testing cows and people for the virus, but they take different approaches. Scientists tracking bird flu are increasingly concerned that current surveillance efforts are not sufficient.