The U.S. government failed to eliminate the virus on dairy farms when it was confined to a handful of states. Now at least 875 herds across 16 states have tested positive.
While many may believe the days of pandemics are behind us, a new bird flu epidemic could threaten that assumption, leading to more economic turbulence.
Doctors say the case of a teen left in critical condition shows H5N1 "can cause severe human illness." Mutations in the virus are deepening concerns about the spread of H5N1.