And next now, we go to Africa, where tonight, two Americans are fighting for their lives, infected with the deadly ebola virus. Friends and family here in the U.S., asking everyone to pray for their... See More
And next now, we go to Africa, where tonight, two Americans are fighting for their lives, infected with the deadly ebola virus. Friends and family here in the U.S., asking everyone to pray for their recovery. ABC's chief medical editor Dr. Richard Besser has been on the front lines of ebola in the past and has the latest tonight. Reporter: Tonight, the condition of the two Americans is deteriorating. Nancy writebol of North Carolina and Dr. Kent Brantly of Texas, in Liberia as medical volunteers for the Christian missionary organization samaritan's purse. You see writebol here, suiting up workers, heading into the ebola ward. And Dr. Brantley, all covered up to treat patients. Today, I spoke with his more, Jan. Ebola broke out in February and Kent chose not to leave but to stay there and do what he could. That didn't surprise us. Reporter: Going into an ebola ward, like I did in Uganda, means taking extreme precautions. There's not one speck of my body that is exposed. Time inside is limited to minutes. Walking out, I was sprayed with disinfectant. In Liberia, that was Nancy writebol's job. But despite the precautions, in this outbreak, the largest in history, more than 1,200 people have been infected. More than half have died. And with ebola, death is gruesome. Victims succumb to internal and external bleeding. But there are survivors. Harrison sakela contracted ebola from his mother. So did the rest of the family. Only I survived, but I lost five person. The mother, my father, the sister, the niece and her daughter. So much concern around the world and rich, a lot of people are worried about it coming into the states through airports. Do have to be worried at an airport? Reporter: This doesn't come at you through the air the way the flu does or measles. You're not going to get this sitting near someone on an airplane. You're not going to get it walking through an airport. You need close physical contact. That's why health care workers and family members are at such great risk. But you need close contact for this to be transmilted. Reporter: That's right.
This transcript has been automatically generated and may not be 100% accurate.