The duration of time between exposure to the virus and the development of symptoms (incubation period) is between 2 to 21 days, usually between 4 to 10 days.However, recent estimates based on mathematical models predict that around 5% of cases may take greater than 21 days to be developed.
Symptoms usually begin with a sudden influenza-like stage characterized by feeling tired, fever, weakness, decreased appetite, muscle pain, joint pain, headache, and sore throat. The fever is usually higher than 38.3 °C (100.9 °F). Most often followed by vomiting, diarrhea and abdominal pain. Next, shortness of breath and chest pain may occur, along with swelling, headaches and confusion. In about half of the cases, the skin may develop a maculopapular rash, a flat red area covered with small bumps, 5 to 7 days after symptoms begin.
In some cases, external and internal bleeding may occur. This typically begins 5 to 7 days after the first symptoms. All infected people show some decreased blood clotting. Bleeding from mucous membranes or from sites of needle punctures has been reported in 40–50 percent of cases. This may cause vomiting blood, coughing up of blood, or blood in stool. Bleeding into the skin may create petechiae, purpura, ecchymoses or hematomas (especially around needle injection sites). Bleeding into the whites of the eyes may also occur. Heavy bleeding is uncommon; if it occurs, it is usually located within the gastrointestinal tract.
Recovery may begin between 7 and 14 days after first symptoms.Death, if it occurs, follows typically six to sixteen days from first symptoms and is often due to low blood pressure from fluid loss. In general, bleeding often indicates a worse outcome, and blood loss may result in death. People are often in a coma near the end of life. Those who survive often have ongoing muscle and joint pain, liver inflammation, decreased hearing, and may have constitutional symptoms such as feeling tired, continued weakness, decreased appetite, and difficulty returning to pre-illness weight. Additionally they develop antibodies against Ebola that last at least ten years, but it is unclear if they are immune to repeated infections. If someone recovers from Ebola, they can no longer transmit the disease.