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Ebola virus disease, known until 2014 as Ebola hemorrhagic (e-BO-luh hehmuh-RAH-jik), fever is a rare viral disease that causes severe internal and external bleeding, and results in death in 50 to 90 percent of those who have been infected. Its contagiousness, high lethality, and short incubation * period (three to eight days on average) have raised fears that it could be used as an agent of bioterrorism.
Although much remains unknown about the Ebola virus and Ebola virus disease, scientists have begun to piece together some of the puzzle. Ebola virus disease was first identified in 1976 in Zaire (now Democratic Republic of the Congo) and was named for a river that flows through that African nation. Part of the Filovirus family, the Ebola virus had as of 2016 five known subtypes, each named for the location in which it was discovered: Zaire, Bundibugyo, Sudan, Reston, and Taï Forest. The Ebola Reston virus, first detected in the United States in 1989, was discovered in sick monkeys imported from the Philippines to a research laboratory in Reston, Virginia. Although a few laboratory workers later showed signs of the virus in their blood, none of them became ill. The Reston strain was assumed to be harmless to humans.
Until 2014, Ebola virus disease was considered rare. With that outbreak, scientists and healthcare personnel worked diligently to control its spread. Efforts were started to develop a vaccine to render the effects of the virus harmless in vaccinated people. In April 2016, a promising vaccine was undergoing clinical trials.
Ebola virus is extremely contagious. It spreads through direct contact with infected blood, especially from contaminated needles, and through contact with the nasal or respiratory secretions of an infected person. Healthcare workers and family members tending to people who have the virus are at the greatest risk of becoming infected and dying of Ebola virus infection. The needles used to take blood samples from patients are an extreme biohazard * because accidental needlesticks expose healthcare workers to the virus and are potentially life-threatening.
Some African cultural traditions may contribute to the spread of the Ebola virus. For example, some funeral rites require a ritual cleansing of the corpse, which can bring the person performing the rite into contact with blood or other body fluids of the deceased. In addition, the Ebola virus infects nonhuman primates such as monkeys and apes. Ape meat is considered a delicacy in parts of Africa, but because of the virus, scientists are recommending that people who live in these regions should avoid eating it. It may contain the Ebola virus.
In the first few days after individuals are infected with the Ebola virus, the symptoms may vary. They often resemble those of many other diseases: fever, severe sore throat, headache, and muscle aches. The early symptoms of Ebola virus disease, however, often progress rapidly to more serious symptoms such as rash, chest pain, severe bloody vomiting and diarrhea, uncontrolled internal bleeding, kidney and liver failure, and shock * .
Doctors can diagnose Ebola virus disease on the basis of the signs and symptoms that appear in patients, as they quickly become ill during outbreaks. Blood tests can sometimes identify the virus directly, or antibodies * to the Ebola virus produced by the body during infection can be detected in the blood. Doctors must be careful when performing tests because simply injecting a needle into a patient who is prone to hemorrhage * can trigger uncontrolled bleeding.
There is no specific medication to treat or cure the Ebola virus after infection occurs. Patients with Ebola virus disease are hospitalized and receive supportive care to treat symptoms. They may receive intravenous * fluids to protect against dehydration * ; monitoring of blood pressure, heart rate, and breathing; and treatment for bleeding or other infections that may develop during the illness. During past outbreaks, 50 to 90 percent of people who developed symptoms of the disease died. Those who survive usually recover in several weeks.
Researchers have discovered a protein on the surface of the Ebola virus that attaches to and damages specific cells of blood vessels. This finding may help to explain the massive bleeding that leads to most Ebola virus deaths.
A vaccine against Ebola known as VSV-EBOV was developed in Canada in 2010 and developed further by an American drug company in 2014. The vaccine underwent Phase I trials on healthy human subjects in Gabon, Kenya, and Germany. It underwent Phase II trials on healthcare workers in Guinea, one of the sites of a deadly outbreak, in 2015. The World Health Organization rated the VSV-EBOV vaccine as “highly effective,” with an effectiveness rate of 100 percent. Phase III trials of the vaccine were ongoing as of January 2016.
See also Bioterrorism Agents: Overview • Fever • Global Health Issues: Overview • Viral Infections
Quammen, David. Ebola: The Natural and Human History of a Deadly Virus. New York: W. W. Norton, 2014.
Willett, Edward. What You Can Do about Ebola. New York: Enslow Publishing, 2016.
Centers for Disease Control and Prevention. “Ebola (Ebola Virus Disease).” http://www.cdc.gov/vhf/ebola/index.html (accessed June 2, 2016).
Centers for Disease Control and Prevention. “Guidance on Personal Protective Equipment (PPE) to Be Used by Healthcare Workers during Management of Patients with Confirmed Ebola or Persons under Investigation (PUIs) for Ebola Who Are Clinically Unstable or Have Bleeding, Vomiting, or Diarrhea in U.S. Hospitals, Including Procedures for Donning and Doffing PPE.” http://www.cdc.gov/vhf/ebola/healthcare-us/ppe/guidance.html (accessed March 15, 2016).
World Health Organization. “Fact Sheet: Ebola Virus Disease.” http://www.who.int/mediacentre/factsheets/fs103/en/ (accessed June 2, 2016).
Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-232-4636. Website: http://www.cdc.gov (accessed March 15, 2016).
Directors of Health Promotion and Education. 1432 K St. NW, Suite 400, Washington, DC 20005. Telephone: 202-659-2230. Website: http://www.dhpe.org (accessed March 15, 2016).
World Health Organization. Avenue Appia 20, 1211 Geneva 27, Switzerland. Telephone: 41-22-791-2111. Website: http://who.int/en/ (accessed June 2, 2016).
* incubation (in-kyoo-BAY-shun) is the period of time between infection by a disease organism and the appearance of the first symptoms. Depending on the organism, this period can extend from hours to months.
* biohazard is a biological agent or condition that poses a threat to humans.
* shock is a serious condition during which blood pressure falls very low and not enough blood flows to the body's organs and tissues. If left untreated, shock may result in death.
* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by such microorganisms as bacteria and viruses.
* hemorrhage (HEH-muh-rij) is uncontrolled or abnormal bleeding.
* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.
* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive loss of body fluids that are not replaced, and occurs through sweating, vomiting, or diarrhea.