On July 22, Brantly woke up feeling feverish. Fearing the worst, Brantly immediately isolated himself. Writebol's symptoms started three days later. A rapid field blood test confirmed the infection in both of them after they had become ill with fever, vomiting and diarrhea.

It's believed both Brantly and Writebol, who worked with the aid organization Samaritan's Purse, contracted Ebola from another health care worker at their hospital in Liberia, although the official Centers for Disease Control and Prevention case investigation has yet to be released.