A fourth farm worker has been infected with bird flu in the growing outbreak linked to dairy cows, health officials reported Wednesday. The worker had direct contact with infected dairy cows on a ...

Bird flu H5N1 is infecting people in the U.S. See the map of cases. Could it trigger the next pandemic? Experts explain the threat and symptoms to watch for.

Bird flu cases are increasing, and a new review suggests the virus might spread between people without causing symptoms. But with limited surveillance and major gaps in data and reporting, the scope ...