Federal authorities say it is likely being carried from farm to farm on objects like farm equipment or clothing that has touched a sick cow.

The U.S. Centers for Disease Control and Prevention says a patient has been hospitalized with a severe case of H5N1 infection in Louisiana, making it the first instance of a severe illness linked to the virus in the United States.

The bird flu outbreak has spread to all 50 states, these maps show. Here are the symptoms and what to do if you think you might be infected.