Several labs will work with federal health authorities to develop a test for avian influenza, as the number of human cases rise across the country.

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.

With the approach of fall and cooler weather across the United States, officials say the risk posed by the H5N1 bird flu virus could rise — and they’re taking steps to prevent the creation of a hybrid flu virus that could more easily infect humans.