A patient in Missouri who was hospitalized after an infection with bird flu had the H5N1 strain of the virus, the US Centers for Disease Control and Prevention confirmed Friday.

Federal officials are still trying to determine how a Missouri resident with no known exposure to bird flu, contracted the virus.

The Centers for Disease Control and Prevention has picked five lab partners to develop a test for avian influenza A(H5N1) — bird flu — including ARUP Laboratories in Salt Lake City. The other lab partners are Quest Diagnostics,