Physician traveled by taxi, subway and went bowling before falling ill

An emergency room doctor who recently returned to New York after treating Ebola patients in West Africa has tested positive for the virus, becoming the first case in the city and the fourth in the United States.

New York Mayor Bill de Blasio and Governor Andrew Cuomo on Thursday urged residents not to be alarmed by the doctor's Ebola diagnosis, even as they described him riding the subway, taking a cab and bowling. De Blasio said all city officials followed "clear and strong" protocols in their handling and treatment of him.