Ebola virus


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Ebola virus

(ēbō`lə), a member of a family (Filovidae) of RNA virusesvirus,
parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
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 that cause hemorrhagic fevers. The virus, named for the region in Congo (Kinshasa) where it was first identified in 1976, emerged from the rain forest, where it survives in as yet unconfirmed hosts, possibly several species of fruit bats but potentially other mammal species; experimental evidence suggests that wild and domestic swine may be a reservoir of the disease. The virus can be fatal to chimpanzees and gorillas as well as humans. In 1989 a similar virus was found in monkeys imported to the United States.

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 vaccine and no cure; a number of treatments for the disease, including a vaccine, are being developed, but they remain experimental.

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.

Bibliography

See D. Quammen, Ebola (2014).

Ebola virus

Ebola viruses are a group of exotic viral agents that cause a severe hemorrhagic fever disease in humans and other primates. The four known subtypes or species of Ebola viruses are Zaire, Sudan, Reston, and Côte d'Ivoire (Ivory Coast), named for the geographic locations where these viruses were first determined to cause outbreaks of disease. Ebola viruses are very closely related to, but distinct from, Marburg viruses. Collectively, these pathogenic agents make up a family of viruses known as the Filoviridae.

Filoviruses have an unusual morphology, with the virus particle, or virion, appearing as long thin rods. A filovirus virion is composed of a single species of ribonucleic acid (RNA) molecule that is bound together with special viral proteins, and this RNA–protein complex is surrounded by a membrane derived from the outer membrane of infected cells. Infectious virions are formed when the virus buds from the surface of infected cells and is released. Spiked structures on the surface of virions project from the virion and serve to recognize and attach to specific receptor molecules on the surface of susceptible cells, allowing the virion to penetrate the cell. The genetic information contained in the RNA molecule directs production of new virus particles by using the cellular machinery to drive synthesis of new viral proteins and RNA. See Ribonucleic acid (RNA), Virus

Although much is known about the agents of Ebola hemorrhagic fever disease, the ecology of Ebola viruses remains a mystery. The natural hosts of filoviruses remain unknown, and there has been little progress at unraveling the events leading to outbreaks or identifying sources of filoviruses in the wild. Fortunately, the incidence of human disease is relatively rare and has been limited to persons living in equatorial Africa or working with the infectious viruses. The virus is spread primarily through close contact with the body of an infected individual, his or her body fluids, or some other source of infectious material.

Ebola virus hemorrhagic fever disease in humans begins with an incubation period of 4–10 days, which is followed by abrupt onset of illness. Fever, headache, weakness, and other flulike symptoms lead to a rapid deterioration in the condition of the individual. In severe cases, bleeding and the appearance of small red spots or rashes over the body indicate that the disease has affected the integrity of the circulatory system. Individuals with Ebola virus die as a result of a shock syndrome that usually occurs 6–9 days after the onset of symptoms. This shock is due to the inability to control vascular functions and the massive injury to body tissues.

It appears that the immune response is impaired and that a strong cellular immune response is key to surviving infections. This immunosuppression may also be a factor in death, especially if secondary infections by normal bacterial flora ensue. See Immunosuppression

Outbreaks of Ebola virus disease in humans are controlled by the identification and isolation of infected individuals, implementation of barrier nursing techniques, and rapid disinfection of contaminated material. Diagnosis of Ebola virus cases is made by detecting virus proteins or RNA in blood or tissue specimens, or by detecting antibodies to the virus in the blood.

Dilute hypochlorite solutions (bleach), 3% phenolic solutions, or simple detergents (laundry or dish soap) can be used to destroy infectious virions. No known drugs have been shown to be effective in treating Ebola virus (or Marburg virus) infections, and protective vaccines against filoviruses have not been developed.

References in periodicals archive ?
This study provides important new information about the persistence of Ebola virus in semen and helps us make recommendations to survivors and their loved ones to help them stay healthy.
To model the introduction of CCCs, we assumed that Ebola virus-susceptible persons could also become infected with other febrile diseases that have Ebola virus disease-like symptoms, which we assumed had symptoms that lasted an average of 7 days.
Secretary Health Jawad Rafiq Malik said that guidelines of World Health Organization being followed for checking Ebola virus and guidance will be sought from the delegation for taking more steps in this regard.
CDC Health Care Provider Preparedness Checklist for Ebola Virus Disease (PDF).
It was told in the meeting that Ebola virus was a fatal disease in which 70 to 80 percent death rate had been recorded.
Earlier in August, the Algerian health authorities said a wide scale preventive measures have been taken on the southern border of the country to counter the spread of deadly Ebola virus.
Concerns were raised over the potential role that dogs could play in the spread of Ebola Virus.
They reported on Russian news channels yesterday they expect coming of Ebola virus before the end of this month.
The representatives of the maritime travel and tourism and shipping agents pointed out that there is no direct maritime routes between the Sultanate and West African countries, afflicted with Ebola Virus.
August 28, 2014 (KHARTOUM) -- The Darfur Regional Authority (DRA) announced that a "weakly suspected" Ebola virus case was infected with HIV.
SPREADING AWARENESS: Participants listen to a lecture on the Ebola virus during an awareness campaign launched by the Zamzam charitable organization in Jeddah on Wednesday.
New Delhi, Aug 6 ( ANI ): Asserting that the risk of Ebola virus cases in India is low, Union Health Minister Dr.