The Centers for Disease Control and Prevention says H5N1 has caused a Louisiana patient to have a severe illness, marking the first ever severe human case in the U.S. According to the CDC, the individual had exposure to sick and dead birds within backyard flocks.

The United States has confirmed its first known severe human infection of H5N1 bird flu, in a person in Louisiana believed to have contracted the virus through contact with sick or dead birds in a backyard flock.