Several strains of the virus found in Africa cause hemorrhagic fever; one found in the W Pacific does not. Once a person is infected with the virus, the disease has an incubation period of 2–21 days; however, some infected persons are asymptomatic. Initial symptoms are sudden malaise, headache, and muscle pain, progressing to high fever, vomiting, severe hemorrhaging (internally and out of the eyes and mouth) and in 50%–90% of patients, death, usually within days. The likelihood of death is governed by the virulence of the particular Ebola strain involved. Ebola virus is transmitted in body fluids and secretions; it may possibly also be transmitted through the air by aerosol droplets. There is no cure. A vaccine, rVSV-ZEBOV, has been developed against the strain that caused the 2013–15 West African outbreak. It was effective, but it was experimental and saw limited use during the outbreak. It is unclear if the protection provided by the vaccine will be long lasting.
Outbreaks of Ebola virus in humans have typically occurred in tropical rainforest regions in Central and West Africa. Among the countries affected have been Congo-Kinshasa (then Zaïre) and Sudan (in a region now in South Sudan), where outbreaks occurred in 1976 and 1979; since then other outbreaks have occurred in Gabon, Uganda, and both Congos. The largest and deadliest outbreak began in late 2013 in Guinea and spread to neighboring Liberia and Sierra Leone, with a few cases in some nearby African nations and in the United States and Europe; some 11,300 people—many more than in any prior outbreak—died in the following two years. Outbreaks have been exacerbated by underequipped and understaffed medical facilities, families caring for patients at home, suspicions that medical personnel are spreading the disease, and other factors.
See D. Quammen, Ebola (2014).
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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