Ebola causes

Overview
Ebola hemorrhagic fever (Ebola fever) is caused by a virus belonging to the family called Filoviridae. Scientists have identified four types of the Ebola virus. Three have been reported to cause disease in humans: Ebola-Zaire virus, Ebola-Sudan virus, and Ebola-Ivory Coast virus. The human disease has so far been limited to parts of Africa.

A very small number of people in the United States who were infected with the fourth type of the virus, known as Ebola Reston, did not develop any signs of disease.

The disease can be passed to humans from infected animals and animal materials. Ebola can also be spread between humans by close contact with infected bodily fluids or through infected needles in the hospital.

Viral reservoirs
Despite numerous studies, the wildlife reservoir of Ebolavirus has not been identified. Between 1976 and 1998, from 30,000 mammals, birds, reptiles, amphibians, and arthropods sampled from outbreak regions, no Ebolavirus was detected apart from some genetic material found in six rodents (Mus setulosus and Praomys species) and a shrew (Sylvisorex ollula) collected from the Central African Republic in 1998. Ebolavirus was detected in the carcasses of gorillas, chimpanzees and duikers during outbreaks in 2001 and 2003 (the carcasses were the source of the initial human infections) but the high mortality from infection in these species precludes them from acting as reservoirs.

Plants, arthropods, and birds have also been considered as reservoirs, however bats are considered the most likely candidate. Bats were known to reside in the cotton factory in which the index cases for the 1976 and 1979 outbreaks were employed and have also been implicated in Marburg infections in 1975 and 1980. Of 24 plant species and 19 vertebrate species experimentally inoculated with Ebolavirus, only bats became infected. The absence of clinical signs in these bats is characteristic of a reservoir species. In 2002-03, a survey of 1,030 animals from Gabon and the Republic of the Congo including 679 bats found Ebolavirus RNA in 13 fruit bats (Hyspignathus monstrosus, Epomops franquetti and Myonycteris torquata). Bats are also known to be the reservoirs for a number of related viruses including Nipah virus, Hendra virus and lyssaviruses.

Bats
Even though rabies and histoplasmosis can be found all over the world, some diseases associated with bats are found exclusively in certain regions of the world. Notably, research suggests that bats might be the source of several hemorrhagic fevers, which affect multiple organ systems in the body and often lead to life-threatening diseases.

One of these diseases is Marburg hemorrhagic fever, which is found exclusively in Africa. Past outbreaks have shown that Marburg Hemorrhagic Fever kills up to 90% of those infected.

While the natural host had for years been unknown, new research suggests that fruit bats are a natural source of this virus, and the virus has been isolated repetitively from fruit bats in Uganda.

The same may be true for Ebola hemorraghic fever. The virus that causes this disease is often referred to as the "cousin" of Marburg virus, since they are the only distinct viruses that belong to a group of viruses known as filoviruses. Like Marburg, Ebola is highly fatal and is found mostly in Africa. Recent studies indicate that, as with Marburg, bats are likely to be a natural source of this virus, although no Ebola virus has been isolated from bats.