The US Centers for Disease Control and Prevention is urging hospitals to accelerate advanced testing of people they suspect may have bird flu.

The CDC is now calling for subtyping of influenza A viruses in all hospitalized patients -- and on an accelerated timeline, ideally within 24 hours. Nirav Shah, MD, JD, principal deputy director of the CDC,

CDC officials say they extended the guidance now because they are seeing more H5N1 patients whose illness they cannot track back to an infected bird or cow.