The incubation period is the time between infection (when a person takes in the virus) and when they start to feel ill. For Ebola, the period can range from 2 to 21 days. However, on average, it is about 7-9 days.
Usually, the person suddenly feels weak, with a fever, muscle/joint pain, headache and sore throat. Vomiting, diarrhea, rash and abdominal pain follow in most cases. Some people may develop redness of eyes and hiccups.
Organ failure and bleeding (both internally and externally) occur in some people. These lead to death. About 50% to 90% of cases are fatal. The Zaire strain is the most lethal strain of Ebola. It is responsible for the current Ebola outbreak.