In Proceedings of the National Academy of Sciences (PNAS), they say that flu-carrying birds may change migratory patterns during La Nina conditions.

BBC: La Nina 'linked' to flu pandemics

Last year a new strain of H3N8 flu jumped from birds to mammals and was responsible for the death of more than 160 seals off the New England coast.

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But the virus doesn't appear to notably sicken infected birds, unlike H5N1, another avian-flu virus that is deadly in birds and occasionally infects people.

WSJ: Bird Flu Found Outside China's Mainland

All flu viruses jump from birds to pigs to humans.

FORBES: Why One Great Vaccine Researcher Wasn't Afraid Of Bird Flu

Angry Birds has spread, like bird flu, from Helsinki to mobile phones to the Web and at this very moment to the Amazon jungle.

FORBES: Audacious Birds

There is also great concern that flu might be carried to poor African nations by migrating birds.

ECONOMIST: Calls for more money as the threat looms ever larger | The

That has led to concerns that the birds used to make the eggs themselves could succumb to bird flu. (The companies emphasize that the chickens are kept under extremely secure conditions.) There is research going on to use dog, monkey or human cell cultures to produce flu shots, but such production is five to ten years away.

FORBES: Flu Shot Gold Rush

Earlier, the commission slapped a ban on all imports of live birds and untreated feathers from both Turkey and Romania, where bird flu was also detected.

ECONOMIST: Devastation in Kashmir

Experts urged Chinese health authorities to keep testing healthy birds, saying the H7N9 virus can infect birds without causing disease, making it harder to detect than the H5N1 bird flu virus that is more familiar to Asian countries.

NPR: China Kills Market Birds As Flu Found In Pigeons