Health officials say they don’t know how a Missouri person caught bird flu, but they believe it may be a rare instance of a “one-off,” stand-alone illness. In a call with reporters Thursday, officials said they have not yet determined how to the person caught the virus. They also have not been able to confirm the exact strain of flu. The case raised questions about the possibility of human-to-human transmission, but they say there is no evidence of that. Unusual flu strains that come from animals are occasionally found in people. This year alone, health officials identified seven human cases of swine flu in the U.S.
