And a particularly ominous strain of avian influenza that has devastated poultry flocks in Asia seems poised to wreak havoc in humans.

In the present outbreaks, however, asymptomatic domestic ducks can directly introduce the virus, in its highly pathogenic form, to poultry flocks.

So far, most human cases have occurred in rural or semirural areas where many households keep small free-roaming poultry flocks that sometimes enter homes.

Because of this, people getting sick with H5N1 from direct contact with infected birds may also continue in countries where poultry flocks are infected.

Germany is preparing to kill at least some of the 400,000 domestic birds on the island to make sure the virus does not spread into poultry flocks, local authorities said.

A lethal form of avian flu has rooted itself deeply into the poultry flocks of poor Asian countries that will have a hard time eradicating it.

The virus has decimated poultry flocks in Asia and has prompted the killing of more than 25 million birds.

All at once Sorka remembered that long-ago day when she had first witnessed the dragonets defending the poultry flocks.

The F.D.A. should ban the use of fluoroquinolones in poultry flocks and the addition of human-use antibiotics to livestock feed.

Then in June, Indonesia reported an outbreak of avian influenza in poultry flocks to the World Organization for Animal Health.