A Utah research laboratory may play a key role in advancing bird flu testing amid an outbreak in commercial and backyard poultry flocks.

A close contact of someone with bird flu became ill on the same day, the C.D.C. reported. But the second person was not tested, and the cause of the illness is unknown.

The H5N1 bird flu has been spreading widely among wild birds, poultry, cows and a growing number of other animals NBC Universal, Inc. Health officials on Thursday said they don’t know how a Missouri person caught bird flu but believe it may be a rare ...