avian flu

Amy Mayer / Harvest Public Media

Since a highly contagious strain of bird flu was found in the U.S. in December, many countries have closed their doors to chickens and turkeys raised here.

The virus isn’t harmful to humans and, so far, only wild birds and backyard flocks have been infected. But commercial poultry farmers are worried because they have the most to lose.

The United Nations' Food and Agriculture Organization warned in August about “a possible major resurgence” of the bird flu because a mutant form of the virus was recently found in Vietnam and Cambodia. Other flu viruses, including strains of swine flu, are occasionally resurfacing in different parts of the world.