What Is the Ebola Virus?

Ebola virus is a type of RNA virus that causes the disease known as Ebola hemorrhagic fever (also known as Ebola).

<>Where Did Ebola Virus Get Its Name?

</Ebola virus got its name from a river in the Democratic Republic of the Congo (formerly Zaire), in Africa, where it was first recognized.


</Ebola virus is one of two members of a family of RNA viruses called the Filoviridae. There are four identified subtypes of Ebola virus. Three of the four have caused disease in humans:

  • Ebola-Zaire
  • Ebola-Sudan
  • Ebola-Ivory Coast.

The fourth Ebola virus subtype, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.

<>Where Does the Virus Come From?

</>The exact origin, locations, and natural habitat (known as the natural reservoir) of Ebola virus remain unknown; however, on the basis of available evidence, and the nature of similar viruses, researchers believe that the virus is zoonotic (animal-borne) and is normally maintained in an animal host that is native to the African continent. Ebola research scientists continue to search for the exact animal host.

A similar host is probably associated with Ebola-Reston, which was isolated from infected cynomolgus monkeys that were imported to the United States and Italy from the Philippines. The Ebola virus is not known to be native to other continents, such as North America


Outbreaks of Ebola Virus

Ebola outbreaks typically appear sporadically. Confirmed cases of Ebola virus infections have been reported in:

  • The Democratic Republic of the Congo
  • Gabon
  • Sudan
  • The Ivory Coast
  • Uganda.

Ebola in the United States

In the United States, there have been no reported cases of Ebola virus infections in humans. Ebola-Reston virus caused severe illness and death in monkeys imported to research facilities in the United States and Italy from the Philippines; during these Ebola outbreaks, several research workers became infected with the virus, but did not become ill.

How Do Outbreaks of Ebola Virus Begin?

Just as scientists are unsure of the animal host for the Ebola virus, they are also unsure how an Ebola virus outbreak occurs; however, researchers have hypothesized that the first patient with Ebola becomes infected with Ebola virus through contact with an infected animal.

How Is It Transmitted?

Once transmission of Ebola virus occurs to the first human, scientists do know how Ebola virus is spread from human to human. They know that transmission of Ebola occurs through direct contact with patients who have Ebola, or direct contact with their body fluids (such as blood or secretions). Transmission of Ebola occurs most often when an infected person is in the late stages of Ebola hemorrhagic fever.

Ebola Virus as a Biological Weapon

In the aftermath of the events of September and October, 2001, there is heightened concern that the Ebola virus might be used as an agent of bioterrorism. The deliberate release of Ebola virus is now regarded as a possibility, and the United States is taking precautions to deal with this possibility.

The Centers for Disease Control and Prevention (CDC) calls the Ebola virus a Category A agent. Category A agents are believed to present the greatest potential threat for harming public health, and have a moderate to high potential for large-scale dissemination (spread). The public is generally more aware of category A agents, and broad-based public health preparedness efforts are necessary. Other Category A agents are:

  • Anthrax
  • Plague
  • Botulism (food poisoning from ingesting improperly canned, or preserved, food)
  • Tularemia (disease transmitted through the bite of an infected insect, or animal)