By LAURA UNGAR, AP Science Writer A genetic analysis suggests the bird flu virus mutated inside a Louisiana patient who contracted the nation’s first severe case of the illness, the U.S. Centers for Disease Control and Prevention said this week. Scientists believe the mutations may allow the virus to better bind to receptors in the upper airways of humans — something they say is concerning but not a cause for alarm. Michael Osterholm, a University of Minnesota infectious disease researcher, likened this binding interaction to a lock and key.