The world is currently fighting Coronavirus which has similar case with the deadly Ebola hemorrhagic fever outbreak of 2014. See what you never knew about Ebola Virus Disease.

Origin

Ebola virus disease (EVD), one of the deadliest viral diseases, was discovered in 1976 when two consecutive outbreaks of fatal hemorrhagic fever occurred in different parts of Central Africa. The first outbreak occurred in the Democratic Republic of Congo (formerly Zaire) in a village near the Ebola River, which gave the virus its name. The second outbreak occurred in what is now South Sudan, approximately 500 miles (850 km) away.

Initially, public health officials assumed these outbreaks were a single event associated with an infected person who traveled between the two locations. However, scientists later discovered that the two outbreaks were caused by two genetically distinct viruses: Zaire ebolavirus andSudan ebolavirus. After this discovery, scientists concluded that the virus came from two different sources and spread independently to people in each of the affected areas.

Viral and epidemiologic data suggest that Ebola virus existed long before these recorded outbreaks occurred. Factors like population growth, encroachment into forested areas, and direct interaction with wildlife (such as bushmeat consumption) may have contributed to the spread of the Ebola virus.

Hosts

Following the discovery of the virus, scientists studied thousands of animals, insects, and plants in search of its source (called reservoir among virologists, people who study viruses). Gorillas, chimpanzees, and other mammals may be implicated when the first cases of an EVD outbreak in people occur. However, they – like people – are “dead-end” hosts, meaning the organism dies following the infection and does not survive and spread the virus to other animals. Like other viruses of its kind, it is possible that the reservoir host animal of Ebola virus does not experience acute illness despite the virus being present in its organs, tissues, and blood. Thus, the virus is likely maintained in the environment by spreading from host to host or through intermediate hosts or vectors.

African fruit bats are likely involved in the spread of Ebola virus and may even be the source animal (reservoir host). Scientists continue to search for conclusive evidence of the bat’s role in transmission of Ebola. The most recent Ebola virus to be detected, Bombali virus, was identified in samples from bats collected in Sierra Leone.

History of Ebola Outbreaks

Since its discovery in 1976, various cases of Ebola Virus Disease have occurred in Africa. The 2014-2016 Ebola outbreak in West Africa began in a rural setting of southeastern Guinea, spread to urban areas and across borders within weeks, and became a global epidemic within months.

Different Species Of Ebola Virus

  • Ebola virus (species Zaire ebolavirus)
  • Sudan virus (species Sudan ebolavirus)
  • Taï Forest virus (species Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus)
  • Bundibugyo virus (species Bundibugyo ebolavirus)
  • Reston virus (species Reston ebolavirus)
  • Bombali virus (species Bombali ebolavirus)

Of these, only four (Ebola, Sudan, Taï Forest, and Bundibugyo viruses) are known to cause disease in people. Reston virus is known to cause disease in nonhuman primates and pigs, but not in people. It is unknown if Bombali virus, which was recently identified in bats, causes disease in either animals or people.

Ebola virus was first discovered in 1976 near the Ebola River in what is now the Democratic Republic of Congo. Since then, the virus has been infecting people from time to time, leading to outbreaks in several African countries. Scientists do not know where Ebola virus comes from. However, based on the nature of similar viruses, they believe the virus is animal-borne, with bats or nonhuman primates with bats or nonhuman primates (chimpanzees, apes, monkeys, etc.) being the most likely source. Infected animals carrying the virus can transmit it to other animals, like apes, monkeys, duikers and humans.

The virus spreads to people initially through direct contact with the blood, body fluids and tissues of animals. Ebola virus then spreads to other people through direct contact with body fluids of a person who is sick with or has died from EVD. This can occur when a person touches these infected body fluids (or objects that are contaminated with them), and the virus gets in through broken skin or mucous membranes in the eyes, nose, or mouth. People can get the virus through sexual contact with someone who is sick with EVD, and also after recovery from EVD. The virus can persist in certain body fluids, like semen, after recovery from the illness.

Ebola survivours may experience side effects after their recovery, such as tiredness, muscle aches, eye and vision problems and stomach pain.

Symptoms Of Ebola

The time interval from infection with Ebola to the onset of symptoms is 2-21 days, although 8-10 days is most common. Signs and symptoms include:

  • fever
  • headache
  • joint and muscle aches
  • weakness
  • diarrhea
  • vomiting
  • stomach pain
  • lack of appetite

Some patients may experience:

  • rash
  • red eyes
  • Hiccups
  • cough
  • sore throat
  • chest pain
  • difficulty breathing
  • difficulty swallowing
  • bleeding inside and outside of the body

Laboratory tests may show low white blood cell and platelet counts and elevated liver enzymes. As long as the patient’s blood and secretions contain the virus, they are infectious. In fact, Ebola virus was isolated from the semen of an infected man 61 days after the onset of illness.

Mode Of Transmission of Ebola

  • Direct contact through broken skin and mucous membranes with the blood, secretions, organs, or other body fluids of infected people.
  • Indirect contact with environments contaminated with such fluids.
  • Exposure to contaminated objects, such as needles.
  • Burial ceremonies in which mourners have direct contact with the body of the deceased.
  • Exposure to the semen of people with Ebola or who have recovered from the disease – the virus can still be transmitted through semen for up to 7 weeks after recovery from illness.
  • Contact with patients with suspected or confirmed EVD – healthcare workers have frequently been infected while treating patients.

There is no evidence that Ebola can be spread via insect bites.

Risk Factors

The risk of contracting Ebola is low. There is a higher risk of becoming infected when:

  • Traveling to areas of Africa where there have been confirmed cases of Ebola.
  • Conducting animal research with monkeys imported from Africa or the Philippines.
  • Providing medical or personal care to people who may have been exposed to Ebola.
  • Preparing people for burial who have been infected with Ebola.

Tests and diagnosis

According to the WHO, samples from patients with Ebola are an extreme biohazard risk. Testing should be conducted under maximum biological containment conditions.

Before Ebola can be diagnosed, other diseases should be ruled out, and, if Ebola is suspected, the patient should be isolated. Public health professionals should be notified immediately. Ebola virus infections can be diagnosed definitively in a laboratory through several types of tests, including:

  • Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing.
  • IgM ELISA.
  • Polymerase chain reaction (PCR).
  • Virus isolation.

In the more advanced stages of the disease or after recovery, diagnosis is made using IgM and IgG antibodies. Ebola can be diagnosed retrospectively in deceased patients by other forms of testing.

Ebola vaccines

In October 2014, the World Health Organization (WHO) organized an expert consultation to assess, test, and eventually license two promising Ebola vaccines:

  • cAd3-ZEBOV – GlaxoSmithKline has developed this vaccine in collaboration with the United States National Institute of Allergy and Infectious Diseases (NIH). It uses a chimpanzee-derived adenovirus vector with an Ebola virus gene inserted.
  • rVSV-ZEBOV – this was developed by the Public Health Agency of Canada in Winnipeg with NewLink Genetics, a company, located in Ames, IA. The vaccine uses a weakened virus found in livestock; one of its genes has been replaced by an Ebola virus gene.

On July 31 2015, Lancet published preliminary results of a vaccine trial funded and organized by the WHO; the Ebola ca Suffit vaccine had 100 percent efficacy in the trial, which took place in Guinea and involved 4,000 people. The full results of this trial were published in Lancet in February 2017.

The next step is to make these vaccines available as soon as possible – and in sufficient quantities – to protect critical frontline workers and to make a difference in the epidemic’s future evolution.

Prevention/Control

Preventing transmission is achieved by:

  • ensuring all healthcare workers wear protective clothing
  • implementing infection-control measures, such as complete equipment sterilization and routine use of disinfectant
  • isolation of Ebola patients from contact with unprotected persons

Thorough sterilization and proper disposal of needles in hospitals are essential in preventing further infection and halting the spread of an outbreak.

Ebola tends to spread quickly through families and among friends as they are exposed to infectious secretions when caring for an ill individual. The virus can also spread quickly within healthcare settings for the same reason, highlighting the importance of wearing appropriate protective equipment, such as masks, gowns, and gloves.

Together with the WHO, the Centers for Disease Control and Prevention (CDC) has developed a set of guidelines to help prevent and control the spread of Ebola – Infection Control for Viral Hemorrhagic Fevers In the African Healthcare Setting.

References

1. Baseler L., Chertow D, et. Al. The Pathogenesis of Ebola Virus Disease. Annu. Rev. Pathol. Mech. Dis. 2017. 12:387–418.

2. Goldstein T. et al. The discovery of Bombali virus adds further support for bats as hosts of ebolavirusesExternal

3. Nature Microbiology.2018 Aug 27. [Epub ahead of print]Amundsen, S. Historical Analysis of the Ebola Virus: Prospective Implications for Primary Care Nursing Today. Clinical Excellence for Nurse Practitioners. Vol 2. No 6. 1998. 343-351.

4. Baseler L., Chertow D, et. Al. The Pathogenesis of Ebola Virus Disease. Annu. Rev. Pathol. Mech. Dis. 2017. 12:387–418.

5. Amundsen, S. Historical Analysis of the Ebola Virus: Prospective Implications for Primary Care Nursing Today. Clinical Excellence for Nurse Practitioners. Vol 2. No 6. 1998. 343-351.

6.WHO. Health worker Ebola infections in Guinea, Liberia and Sierra Leone: A Preliminary Report 21 May 2015. Accessed June 20, 2017. http://www.who.int/hrh/documents/21may2015_web_final.pdf

7.Khan A. et al. The Reemergence of Ebola Hemorrhagic Fever, Democratic Republic of the Congo, 1995. J Infect Dis (1999) 179 (Suppl 1): S76-86.

8. Baseler L., Chertow D, et. Al. The Pathogenesis of Ebola Virus Disease. Annu. Rev. Pathol. Mech. Dis. 2017. 12:387–418.

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