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, U.S. health officials said on Friday.

In what could be the first cases of bird flu spreading between humans in the United States, a group of potential H5N1 infections in Missouri has now grown to eight. However, state health officials are still awaiting antibody tests to confirm whether the H5N1 infection is growing,

A total of 94 healthcare workers were possibly exposed to the state's first human bird flu case, and the nation's first without animal contact.

After a patient with bird flu was hospitalized last month, state and federal health officials first determined the patient may have infected one household member and two hospital workers. However, "Missouri has since identified four additional health care workers who later developed mild respiratory symptoms,

Four more health care workers are being treated for respiratory symptoms after being exposed to bird flu - bringing the total number of possible cases to seven. Emory's Dr. Neil Winawer discusses the significance of the recent findings with Alyse Eady.