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 (formerly Zaire) 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 four identified subtypes of Ebola virus. Three of the four have caused disease in humans: Ebola-Zaire, Ebola-Sudan, and Ebola-Ivory Coast. The fourth, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.

Causes

Ebola hemorrhagic fever is caused by the Ebola virus. Humans can get the virus through contact with infected animals, humans, or needles. 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. A similar host is probably associated with Ebola-Reston 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.

Risk Factors

The following factors increase your chances of developing Ebola hemorrhagic fever. If you have any of these risk factors, tell your doctor:

• Travel to an area where an outbreak has occurred (almost all cases of Ebola hemorrhagic fever have occurred in Africa; no cases have ever been reported in the United States.)

• Exposure to healthcare settings in which a person with Ebola hemorrhagic fever has been treated

• Contact with another person who has Ebola hemorrhagic fever

Symptoms

The incubation period for Ebola HF ranges from 2 to 21 days. The onset of illness is abrupt and is characterized by fever, headache, joint and muscle aches, sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. A rash, red eyes, hiccups and internal and external bleeding may be seen in some patients.

Researchers do not understand why some people are able to recover from Ebola HF and others are not. However, it is known that patients who die usually have not developed a significant immune response to the virus at the time of death.

Diagnosis

Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing, IgM ELISA, polymerase chain reaction (PCR), and virus isolation can be used to diagnose a case of Ebola HF within a few days of the onset of symptoms. Persons tested later in the course of the disease or after recovery can be tested for IgM and IgG antibodies; the disease can also be diagnosed retrospectively in deceased patients by using immunohistochemistry testing, virus isolation, or PCR.

Treatment

There is no cure for Ebola hemorrhagic virus. Your treatment will include therapy for symptoms you are experiencing, which may include intravenous management of your fluids and electrolytes, oxygen and blood pressure support, and treatment for any complicating infections.

Prevention

To help reduce your chances of getting Ebola hemorrhagic fever, take the following steps:

• Avoid traveling to an area that is experiencing an outbreak.

• If you are a healthcare worker, wear protective clothing, such as masks, gloves, gowns, and goggles, and avoid reusing needles.

• Avoid contact with anyone who may have been exposed to the Ebola virus.

RESOURCES:

Centers for Disease Control and Prevention
http://www.cdc.gov

World Health Organization
http://www.who.int

CANADIAN RESOURCES:

Health Canada
http://www.hc-sc.gc.ca

Public Health Agency of Canada
http://www.phac-aspc.gc.ca

References:

Ebola hemorrhagic fever. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola.htm. Accessed September 25, 2006.