Transcript for Ebola Hits Home
And we begin with new developments as we come on the air this evening in that first case of ebola, diagnosed here in the U.S. And tonight, the first images of the patient. His name is Thomas Eric Duncan. He was visiting family in Dallas. This evening, all eyes on that hospital in Dallas. He's fighting for his life amid new questions about why he was sent home the first time he went to the hospital, telling nurses he felt sick. Meantime, elsewhere in that city, letters going home to parents. Schools being cleaned. Extra precautions being taken this evening as authorities try to track down everyone this man came into contact with. Dr. Richard Besser standing by with your questions about the flights he took, about schools. But first, ABC's Cecilia Vega right there at the hospital. Good evening. Reporter: David, good evening to you. That patient being treated in this hospital, right behind me and tonight, that very hospital facing tough questions about how it handled this case. Potentially exposing others to this deadly disease. Tonight, in this Dallas hospital, Thomas Eric Duncan desperately ill. Doctors saying he is in serious condition, but awake and asking for food. Quarantined in total isolation inside, while outside, the city of Dallas is on high alert. This is all hands on deck. Reporter: Disease detectives from the CDC now here on the ground, in a race to find out if Duncan spread ebola to anyone else. Tracing his path from the hot zone in west Africa, this much they know. His journey begins on the 19th of September, day one. Already infected, but no obvious symptoms, he leaves Liberia. At the airport screening, like every other passenger, his temperature probably taken with an infrared thermometer. But no fever yet. So, he boards a plane, flying to Brussels, then getting on a united airlines flight, full of passengers. The next day, arriving in Dallas, heading to this apartment complex to visit family. Including several children. Still, no signs of ebola. But four days later, he starts getting sick. And that's when ebola becomes contagious. Just over 24 hours later, he's so ill, he walks into this Dallas emergency room, telling a nurse he'd travels from west Africa. But here, the critical breakdown. That nurse didn't pass the information along and he's sent home. Three days later, he is back at the hospital, this time, rushed by ambulance, fighting for his life. Are the people of Dallas, the people of Texas, here in the U.S., are we safe from ebola? I have all confidence in the CDC that we have contained this vile us are within the number of people that we're looking at now. Reporter: Investigators monitoring up to 18 people in all. From the three emts who first treated Duncan in the ambulance to the doctors and nurses in the emergency room and his family, adults and five children potentially exposed. Their schools alerted, even scrubbed down today. Somewhere inside this apartment complex where the man was visiting family are his relatives, potentially exposed to ebola. And right now, they have been told not to leave. No work, no school, for 21 days. Neighbors here, worried. I am scared, because there's a lot of children out here and, you know, a lot of this, this is something new to us. This is scary, I every thought it would come here in the united States. Reporter: Some schools sent letters to parents today alerting them of the situation and in a sign of just how nervous some people are, some parents say they are pulling their kids out of school tomorrow. In the meantime, Dallas county health officials told me today they would not be surprised if a second person with ebola comes forward. David? Cecilia Vega, thank you. I want to get right to Dr. Richard Besser in the hot zone tonight, Liberia. The heart of this ebola outbreak. And rich, first off, so many questions from our viewers tonight. First, the breakdown, it would seen. His first trip to that Dallas hospital, he'd said he'd be in Liberia, that's what he told nurses there, but he was sent home. How does this happen? Reporter: David, that is the critical breakdown. If you get that kind of information, you have to act on it. Otherwise, there's no value in it. The investigation tomorrows are going to want to see where the breakdown occurred and can we prevent that from happening in the future. They're going to follow everyone he came in contact with for 21 days, including those five children he was close to. But tonight, word of the ripple effect. Not cleaning schools that those children attended. This is going to alarm a lot of parents, but this is just a precaution, right? Reporter: That's right. Following people for 21 days is how you prevent infection. But these kids did not have symptoms. And you can't transmit the infection until you have those symptoms. So, cleaning the schools will help them sleep better, but there really is no risk at those schools because the kids were well at the time. Rich, we know 43 hours of traveling before this man got back to America. A lot of people still asking about those planes. One viewer tweeting us a common question. If this guy sneezes in an airplane and we're breathing recycled air, can we be affected? David, there are few things here that are reassuring. Sneezing is uncommon in someone who has ebola. And this man, when he was on the plane, he was brewing the infection, but he had no symptoms. He wasn't showing the signs of disease and you can't transmit the disease until you are actually sick. Lastly, on this plane, they've changed the way air flows. So, as it goes through and it circulates, it is filtered. I've traveled this journey, it's so long, and the idea of sitting on a plane with someone who goes on to develop ebola is very frightening. I'm sure it's frightening for everyone who was there.
This transcript has been automatically generated and may not be 100% accurate.