Health authorities in the US are studying seven people who developed influenza symptoms after being exposed to a Missouri bird flu patient, raising the possibility of the first human-to-human transmission of the infection.

A possible cluster of bird flu infections has grown to include eight people, in what may be the first examples of person-to-person transmission in the U.S.

Health officials are investigating whether a person in Missouri who was hospitalized with bird flu in early September might have infected a handful of others. Testing is ongoing among five health care workers and a household member exposed to the infected person who all came down with mild respiratory symptoms.

By Julie Steenhuysen (Reuters) -Four additional healthcare workers in Missouri who came in contact with a hospitalized bird flu patient developed mild respiratory symptoms but the virus was not confirmed in any of them,

The CDC said an investigation into a human H5N1 bird flu infection in Missouri has found four additional health care workers who fell ill after caring for the patient.