Ebola

Ebola Hemorrhagic Fever
Information Packet

Picture: an Electron Micrograph of the Ebola Virus
Courtesy: Centers for Disease Control and Prevention

2009 Special Pathogens Branch
Division of High-Consequence Pathogens and Pathology
National Center for Emerging Zoonotic Infectious Diseases
Centers for Disease Control and Prevention
U.S. Department of Health and Human Services

EbolaHemorrhagic Fever
Fact Sheet

What is Ebola hemorrhagic fever?
Ebola hemorrhagic fever (Ebola HF) is a severe, often-fatal disease in humans and nonhuman primates (monkeys, gorillas,
and chimpanzees) that has appeared sporadically since its initial recognition in 1976. The disease is caused by infection
with Ebola virus, named after a river in the Democratic Republic of the Congo (formerlyZaire) in Africa, where it was first
recognized. The virus is one of two members of a family of RNA viruses called the Filoviridae. There are five identified
subtypes of Ebola virus. Four of the five have caused disease in humans: Ebola-Zaire, Ebola-Sudan, Ebola-Ivory Coast and
Ebola-Bundibugyo. The fifth, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.

Where is Ebolavirus found in nature?
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 (animalborne) with four of the five subtypes occurring in an animal host native to Africa. A similar host, most likely in thePhilippines, is probably associated with the Ebola-Reston subtype, which was isolated from infected cynomolgous
monkeys that were imported to the United States and Italy from the Philippines. The virus is not known to be native to
other continents, such as North America.

Where do cases of Ebola hemorrhagic fever occur?
Confirmed cases of Ebola HF have been reported in the Democratic Republic ofthe Congo, Gabon, Sudan, the Ivory Coast,
Uganda, and the Republic of the Congo. No case of the disease in humans has ever been reported in the United States.
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 outbreaks, several research workers became infected with the virus, but did notbecome
ill.
Ebola HF typically appears in sporadic outbreaks, usually spread within a health-care setting (a
situation known as amplification). It is likely that sporadic, isolated cases occur as well, but go unrecognized. A
table showing a chronological list of known cases and outbreaks is available below.

How is Ebola virus spread?
Infections with Ebola virus are acute. There is nocarrier state. Because the natural reservoir of the virus is unknown, the
manner in which the virus first appears in a human at the start of an outbreak has not been determined. However,
researchers have hypothesized that the first patient becomes infected through contact with an infected animal.
After the first case-patient in an outbreak setting is infected, the virus can be transmitted in severalways. People can be
exposed to Ebola virus from direct contact with the blood and/or secretions of an infected person. Thus, the virus is often
spread through families and friends because they come in close contact with such secretions when caring for infected
persons. People can also be exposed to Ebola virus through contact with objects, such as needles, that have been
contaminated withinfected secretions.
Nosocomial transmission refers to the spread of a disease within a health-care setting, such as a clinic or hospital. It occurs
frequently during Ebola HF outbreaks. It includes both types of transmission described above. In African health-care
facilities, patients are often cared for without the use of a mask, gown, or gloves. Exposure to the virus has occurred when
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