First case of H5N1 -- or bird flu -- found in US duck

A duck in Washington state has tested positive for a strain of bird flu that's killed hundreds of people overseas.

A green-winged teal tested positive for H5N1 after being shot by a hunter in northern Washington state.

This is the first case of this strain ever seen in the U.S., but it's already circulated across Asia and Egypt.

Researchers say the strain of H5N1 found in the American duck is genetically different from the strain seen overseas, and they don't believe it has infected any people or domestic poultry in the U.S. yet.

But wild birds can infect domestic flocks, which is why agriculture officials are concerned.

A microbiologist who specializes in wildlife disease told NBC right now this is of greater concern to poultry farmers, not the general population: "But because the H5 comes from the Asian H5N1, I would say the risk is not zero."

Still, it's not exactly clear what the risk is. H5N1 doesn't pass easily from human to human, and people, specifically hunters, generally only contract it when they come into contact with an infected bird.

It's rare for humans to contract a bird flu, but when they do, it can be deadly, since the human body doesn't have strong defenses against it.

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