Facts: Ebola hemorrhagic fever is a disease caused by one of five different Ebola viruses. Four of the strains can cause severe illness in humans and animals. The fifth, Reston virus, has caused illness in some animals, but not in humans.
The first human outbreaks occurred in 1976, one in northern Zaire (now Democratic Republic of the Congo) in Central Africa: and the other, in southern Sudan (now South Sudan). The virus is named after the Ebola River, where the virus was first recognized in 1976, According to the Centers for Disease Control and Prevention.
Ebola is extremely infectious but not extremely contagious. It is infectious, because an infinitesimally small amount can cause illness. Laboratory experiments on nonhuman primates suggest that even a single virus may be enough to trigger a fatal infection.
Instead, Ebola could be considered moderately contagious, because the virus is not transmitted through the air.
The most contagious diseases, such as measles or influenza, virus particles are airborne.
Humans can be infected by other humans if they come in contact with body fluids from an infected person or contaminated objects from infected persons. Humans can also be exposed to the virus, for example, by butchering infected animals.
While the exact reservoir of Ebola viruses is still unknown, researchers believe the most likely natural hosts are fruit bats.
Symptoms of Ebola typically include: weakness, fever, aches, diarrhea, vomiting and stomach pain. Additional experiences include rash, red eyes, chest pain, throat soreness, difficulty breathing or swallowing and bleeding (including internal).
Typically, symptoms appear 8-10 days after exposure to the virus, but the incubation period can span two to 21 days.
Unprotected health care workers are susceptible to infection because of their close contact with patients during treatment.
Deadly human Ebola outbreaks have been confirmed in the following countries: Democratic Republic of the Congo (DRC), Gabon, South Sudan, Ivory Coast, Uganda, Republic of the Congo (ROC), Guinea and Liberia.
According to the World Health Organization, "there is no specific treatment or vaccine," and the fatality rate can be up to 90%. Patients are given supportive care, which includes providing fluids and electrolytes and food.
There are five subspecies of the Ebola virus: Zaire ebolavirus (EBOV), Bundibugyo ebolavirus (BDBV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV) and Reston ebolavirus (RESTV)
Statistics: The CDC reports that there have been 5,848 cases of Ebola since 1976, resulting in 3,246 deaths. (as of September 25, 2014)
Timeline: *Includes outbreaks resulting in more than 100 deaths or special cases.
1976 – First recognition of the EBOV disease is in Zaire (now Democratic Republic of the Congo). The outbreak has 318 reported human cases, leading to 280 deaths. An SUDV outbreak also occurs in Sudan (now South Sudan), which incurs 284 cases and 151 deaths.
1989 – In Reston, Virginia, macaque monkeys imported from the Philippines are found to be infected with the Ebola virus (later named the Ebola-Reston virus).
1990 – In Texas and Virginia quarantine facilities, four humans develop Ebola antibodies after contact with monkeys imported from the Philippines. None of the humans has symptoms.
1995 – An outbreak in Democratic Republic of the Congo (formerly Zaire) leads to 315 reported cases and at least 250 deaths.
2000-2001 – A Ugandan outbreak (SUDV) results in 425 human cases and 224 deaths.
2001-2002 – An EBOV outbreak occurs on the border of Gabon and Republic of the Congo (ROC), which results in 53 deaths on the Gabon side and at least 43 deaths on the Republic of the Congo side.
December 2002 - April 2003 – An EBOV outbreak in Republic of the Congo results in 143 reported cases and 128 deaths.
2007 – An EBOV outbreak occurs in the Democratic Republic of the Congo (DRC), 187 of the 264 cases reported result in death. In late 2007, an outbreak in Uganda leads to 37 deaths. 149 cases were reported.
November 2008 – The Ebola-Reston virus (RESTV) is detected in five humans in the Philippines. They are workers on a pig farm and slaughterhouse and suffer no symptoms. This is the first known occurrence of the Reston virus in pigs.
August 26, 2014 – The Ministry of Health in the Democratic Republic of the Congo notifies the World Health Organization of an Ebola outbreak in the country. It is the seventh outbreak in the country since 1976, when the virus was first identified near the Ebola river. The outbreak is not related to the ongoing outbreak in Guinea, Liberia, Nigeria and Sierra Leone. As of September 21, 68 cases and 41 deaths have been reported in the Democratic Republic of the Congo.
2014 West Africa Outbreak: Confirmed or suspected cases of Ebola as of September 21, 2014 (World Health Organization):
Guinea – 1022 cases, 635 deaths
Liberia – 3280 cases, 1677 deaths
Nigeria – 20 cases, 8 deaths
Senegal – 1 case, 0 deaths
Sierra Leone – 1940 cases, 597 deaths