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Ebola
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Ebola hemorrhagic fever (Ebola) is a very contagious illness that is often fatal in humans and nonhuman primates (monkeys, gorillas, and chimpanzees). It has appeared sporadically since it was first recognized in 1976.
The cause of Ebola is an infection with the Ebola virus (see Ebola Pictures). The virus got its name from 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 Filoviridae. There are four identified subtypes of Ebola virus. Three of the four have caused disease in humans:
The fourth Ebola virus subtype, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.
(Click Causes of Ebola for more information on what causes this disease.)
Ebola outbreaks typically appear sporadically. Confirmed cases of Ebola virus infections have been reported in:
No case of Ebola 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 not become ill.
The exact origin, locations, and natural habitat (known as the natural reservoir) of the virus remain unknown; however, on the basis of available evidence, and the nature of similar viruses, researchers believe that the Ebola virus lives in an animal host that is native to the African continent. They continue to search for the exact animal.
Just as scientists are unsure of the animal host for the virus, they are also unsure how an Ebola virus outbreak occurs. Researchers have hypothesized that the first patient with Ebola becomes infected with the Ebola virus through contact with an infected animal.
Once Ebola virus infects the first human, transmission of Ebola continues through direct contact with an infected person, or his or her body fluids (such as blood or secretions). The spread of the virus from an infected person most often occurs during the late stages of an Ebola infection.
(Click Transmission of Ebola for a closer look at how the disease is transmitted.)
When a person becomes infected with Ebola virus, the virus begins to multiply within the body. After four to six days on average, symptoms can begin. The period between infection with Ebola virus and the start of symptoms is called the incubation period. The incubation period for Ebola can be as short as 2 days or as long as 21 days.
(Click Ebola Incubation Period for more information.)
The start of Ebola symptoms is usually abrupt. Symptoms of this disease can include:
(Click Ebola Symptoms for more information on possible signs and symptoms of this illness.)
In order to make a diagnosis, the doctor will ask a number of questions and perform a physical exam. If the doctor suspects an Ebola virus infection, he or she will order labs tests that can identify the virus itself, or antibodies made by the body against the Ebola virus.
Before making an Ebola diagnosis, the doctor will also consider other conditions that can cause similar symptoms. Some of these conditions include:
(Click Ebola Diagnosis for more information.)
There is only one Ebola cure: time. There is currently no proven treatment that can kill the Ebola virus. Treatment for this illness focuses on providing relief of symptoms as the body fights the virus. This is called supportive care.
(Click Ebola Treatment for more information on this topic.)
Death occurs in between 50 to 90 percent of Ebola patients. Research scientists do not understand why some people are able to recover from Ebola hemorrhagic fever and others are not; however, it is known that Ebola victims usually have not developed a significant immune response to the Ebola virus at the time of death.
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 include:
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