Several species of Ebolavirus found in Africa cause Ebola virus disease (formerly known as Ebola hemorrhagic fever); one found in the W Pacific, which was first identified (1989) in monkeys imported into the United States, does not. Once a person is infected, 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, diarrhea, vomiting, symptoms of kidney and liver impairment, and in some cases severe hemorrhaging (internally and out of the eyes and mouth). In 25%–90% of patients, death results, usually within days. The virus is transmitted in body fluids and secretions; it may possibly also be transmitted through the air by aerosol droplets.
A vaccine, rVSV-ZEBOV, has been developed against the species, Zaire ebolavirus, that caused the 2013–15 West African outbreak. It was effective, but it was experimental at the time and saw limited use during that outbreak. Several experimental treatments (an antiviral drug and cloned antibodies) and the vaccine were used in the 2018–19 Congo outbreak, and helped lower fatality rates and protect health-care workers and others in contact with patients. Treatments involved cloned antibodies (REGN-EB3 and mAb114) proved more effective, and were especially effective when begun early. It is unclear if the protection provided by the vaccine will be long lasting. Other vaccines are in development.
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).
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