A patient who may have been exposed to the Ebola virus has been put in isolation at a hospital in Sacramento, California, health group Kaiser Permanente announced Tuesday.
The Centers for Disease Control and Prevention (CDC) will be testing blood samples to rule out the presence of the virus, he said.
Two US patients infected with the virus, a health care worker and a doctor, returned to the United States from Africa for treatment in late July.
Currently there is no approved antiviral treatment or vaccine, only experimental phase treatments.
The global death toll from Ebola stands at 1,229, with the bulk of cases in Liberia, Guinea and Sierra Leone.