What is the Ebola virus?

Mudassir Ali
Mar 10, 2020 06:35 PM 0 Answers
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Mudassir Ali
- Mar 10, 2020 06:35 PM

Originally Answered: What is Ebola virus?
Ebola virus is one of at least 30 known viruses capable of causing viral hemorrhagic fever syndrome. The genus Ebolavirus is currently classified into 5 separate species: Sudan ebolavirus, Zaire ebolavirus, Tai Forest (Ivory Coast) ebolavirus, Reston ebolavirus, and Bundibugyo ebolavirus.

The Ebola virus genome is a single-stranded RNA approximately 19,000 nucleotides long. It encodes seven structural proteins: nucleoprotein (NP), polymerase cofactor (VP35), (VP40), GP, transcription activator (VP30), VP24, and RNA-dependent RNA polymerase.

Ebola virus disease (EVD) first appeared in 1976 in 2 simultaneous outbreaks, one in what is now, Nzara, South Sudan, and the other in Yambuku, Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease has taken its name.

The 2014 outbreak of Ebola virus disease in West Africa, involving Zaire ebolavirus, is the largest outbreak of Ebola virus disease in history.

Ebola virus. Courtesy of the US Centers for Disease Control and Prevention

Signs and symptoms

The following 2 types of exposure history are recognized:

Primary exposure – This typically involves travel to or work in an Ebola-endemic area
Secondary exposure – This refers to human-to-human exposure (eg, medical caregivers, family caregivers, or persons who prepared deceased patients for burial), primate-to-human exposure (eg, animal care workers who provide care for primates), or persons who collect or prepare bush meat for human consumption.
Physical findings depend on the stage of disease at the time of presentation. With African-derived Ebolavirus infection, there is an incubation period (typically 3-8 days in primary cases and slightly longer in secondary cases).

Early findings may include the following:

Severe constitutional signs and symptoms
Maculopapular rash (best seen in white patients)
Bilateral conjunctival injection
Later findings may include the following:
Expressionless facies
Bleeding from intravenous (IV) puncture sites and mucous membranes
Myocarditis and pulmonary edema
In terminally ill patients, tachypnea, hypotension, anuria, and coma.
Survivors of Ebola virus disease have developed the following late manifestations:

Asymmetric and migratory arthralgias
Hearing loss
Unilateral orchitis
Suppurative parotitis

Diagnostic studies that may be helpful include the following:

Basic blood tests – Complete blood count (CBC) with differential, bilirubin, liver enzymes, blood urea nitrogen (BUN), creatinine, pH
Studies for isolating the virus – Tissue culture (only to be performed in one of a few high-containment laboratories throughout the world), reverse-transcription polymerase chain reaction (RT-PCR) assay
Serologic testing – Enzyme-linked immunosorbent assay (ELISA) for antigens or for immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies
Other studies – Immunochemical testing of postmortem skin, electron microscopy.
Prevention and control:

Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation. Community engagement is key to successfully controlling outbreaks. Raising awareness of risk factors for Ebola infection and protective measures that individuals can take is an effective way to reduce human transmission. Risk reduction messaging should focus on several factors:

Reducing the risk of wildlife-to-human transmission from contact with infected fruit bats or monkeys/apes and the consumption of their raw meat. Animals should be handled with gloves and other appropriate protective clothing. Animal products (blood and meat) should be thoroughly cooked before consumption.
Reducing the risk of human-to-human transmission from direct or close contact with people with Ebola symptoms, particularly with their bodily fluids. Gloves and appropriate personal protective equipment should be worn when taking care of ill patients at home. Regular hand washing is required after visiting patients in hospital, as well as after taking care of patients at home.
Reducing the risk of possible sexual transmission, based on further analysis of ongoing research and consideration by the WHO Advisory Group on the Ebola Virus Disease Response, WHO recommends that male survivors of Ebola virus disease practice safe sex and hygiene for 12 months from onset of symptoms or until their semen tests negative twice for Ebola virus. Contact with body fluids should be avoided and washing with soap and water is recommended. WHO does not recommend isolation of male or female convalescent patients whose blood has been tested negative for Ebola virus.
Outbreak containment measures, including prompt and safe burial of the dead, identifying people who may have been in contact with someone infected with Ebola and monitoring their health for 21 days, the importance of separating the healthy from the sick to prevent further spread, and the importance of good hygiene and maintaining a clean environment.
Key facts

Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness in humans.

The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.
The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks.
The first EVD outbreaks occurred in remote villages in Central Africa, near tropical rainforests, but the most recent outbreak in West Africa has involved major urban as well as rural areas.
Community engagement is key to successfully controlling outbreaks. Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation.
Early supportive care with rehydration, symptomatic treatment improves survival. There is as yet no licensed treatment proven to neutralise the virus but a range of blood, immunological and drug therapies are under development.
There are currently no licensed Ebola vaccines but 2 potential candidates are undergoing evaluation.

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