Sept. 19. Thomas Eric Duncan leaves Monrovia, Liberia, for the United States, changing planes in Brussels, Belgium. He has been exposed to Ebola but is not exhibiting symptoms, so he is not contagious. It is unclear whether he knew he had been exposed.
Sept. 20. Duncan arrives in Dallas to visit his sister.
Sept. 24. Duncan's family members tell U.S. authorities this is the day he first felt sick. That is when he likely became contagious.
Sept. 26. Duncan seeks treatment at a Dallas hospital and is sent back to his sister's apartment with antibiotics.
Sept. 28. Duncan is transported to Texas Health Presbyterian Hospital Dallas by ambulance. He is critically ill and put in isolation in the hospital's intensive care unit.