Freetown, Sierra Leone, Jumada I 24, 1436, Mar 15, 2015, SPA -- Ten health care workers with a Boston-based nonprofit organization responding to Sierra Leone's Ebola outbreak are to be evacuated to the United States after one of their colleagues was infected with the deadly disease, AP reported. Partners in Health said in a statement Saturday that the 10, the largest group to be evacuated to the United States over possible Ebola exposure, would travel on non-commercial aircraft and be isolated in Ebola treatment facilities. Four of the 10 health care workers arrived at Nebraska Medical Center in Omaha around 5:30 p.m. Saturday, spokesman Taylor Wilson said Sunday. None of them were sick, but if they do develop Ebola they will be treated in the hospital's specialized biocontainment unit. The others will be monitored at U.S. hospitals with experience treating the disease in Atlanta and in Bethesda, Maryland. -- SPA 20:51 LOCAL TIME 17:51 GMT www.spa.gov.sa/w