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.

Hospitals should expand and speed up testing of people hospitalised with influenza to see if they are suffering from bird flu, according to the Centres for Disease Control and Prevention (CDC).