An additional four American aid volunteers are returning to the U.S. because they may have been exposed to Ebola while helping an American volunteer who contracted the disease, the Centers for Disease Control and Prevention said Tuesday. In total, 16 American volunteers have returned. At least 15 may have been exposed to the often deadly virus when they were trying to help sick colleague, who is now in critical condition at the National Institutes of Health outside Washington. All of the volunteers work for Partners in Health, a nonprofit group helping to fight the Ebola epidemic in West Africa.
