The CDC on Thursday urged labs nationwide to determine within 24 hours of admission whether people hospitalized with the flu have seasonal influenza or are infected with the bird flu that's behind an escalating outbreak in dairy cows and poultry.

The agency is advising enhanced safety measures in Minnesota and South Dakota, where turkey flocks with more than 500 birds should be isolated, monitored and tested for bird flu within 72 hours before going to slaughter,

A child ill with fever and conjunctivitis in San Francisco tested positive for bird flu but had no known source of transmission.