Ebola virus disease

Ebola Virus Disease (END) is a rare and deadly disease in people and nonhuman primates. The viruses that cause END are located mainly in sub-Saharan Africa. People can get END through direct contact with an infected animal (bat or nonhuman primate) or a sick or dead person infected with Ebola virus.

The U.S. Food and Drug Administration (FDA) has approved the Ebola vaccine RSV-ZEBOV (trade name “Bovver”) for the prevention of END. The RSV-ZEBOV vaccine has been found to be safe and protective against only the Zaire retrovirus species of retrovirus.

What is Ebola Virus Disease?

Ebola virus disease (END) is a deadly disease with occasional outbreaks that occur primarily on the African continent. END most commonly affects people and nonhuman primates (such as monkeys, gorillas, and chimpanzees). It is caused by an infection with a group of viruses within the genus Ebola virus:

  • Ebola virus (species Zaire retrovirus)
  • Sudan virus (species Sudan retrovirus)
  • Tao Forest virus (species Ta Forest retrovirus, formerly Cate Ivoire retrovirus)
  • Burgundian virus (species Burgundian retrovirus)
  • Res ton virus (species Res ton retrovirus)
  • Bombastic virus (species Bombastic retrovirus)

Of these, only four (Ebola, Sudan, Tar Forest, and Burgundian viruses) are known to cause disease in people. Res ton virus is known to cause disease in nonhuman primates and pigs, but not in people. It is unknown if Bombastic 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, strikers 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 END. 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 END, and also after recovery from END. The virus can persist in certain body fluids, like semen, after recovery from the illness.

  • Ebola hemorrhagic fever (Ebola virus disease) is a disease caused by four different strains of Ebola virus; these viruses infect humans and nonhuman primates.
  • Compared to most illnesses, Ebola hemorrhagic fever has a relatively short history. Health care professionals discovered Ebola in 1976. There have been several Ebola outbreaks, including the 2014-2016 “unprecedented epidemic” in Africa, which has abated.
  • After an incubation period of 2 to 21 days, symptoms and signs of Ebola virus disease include
    • abrupt fever,
    • headache,
    • joint pain,
    • muscle aches,
    • sore throat, and
    • weakness.
  • Progression of Ebola symptoms includes
    • diarrhea,
    • vomiting,
    • stomach pain,
    • hiccups,
    • rash, and
    • internal and external bleeding.
  • Ebola viruses are mainly found in primates in Africa and the Philippines; there are only occasional Ebola outbreaks of infection in humans. Ebola hemorrhagic fever occurs mainly in Africa in the Republic of the Congo, Gabon, Sudan, Ivory Coast, and Uganda, but it may occur in other African countries.
  • Ebola virus spreads by direct contact with blood and secretions, by contact with blood and secretions that remain on clothing, and by needles and/or syringes or other medical supplies used to treat Ebola-infected patients.
  • Risk factors for Ebola hemorrhagic fever are travel to areas with endemic Ebola hemorrhagic fever and/or any close association with infected people.
  • Early clinical diagnosis is difficult as the symptoms are nonspecific; however, if the patient is suspected to have Ebola, the patient needs to be isolated, and local and state health departments need to be immediately contacted.
  • Definitive diagnostic tests for Ebola hemorrhagic fever are ELISA and/or PCR tests; viral cultivation and biopsy samples may also be used.
  • There is no standard treatment for Ebola hemorrhagic fever; only supportive therapy and experimental treatment is available.
  • There are many complications from Ebola hemorrhagic fever, causing a high mortality rate (reported mortality rates range from 25%-100% with a reported average rate of 40%-50%).
  • Prevention of Ebola hemorrhagic fever is difficult; early testing and isolation of the patient plus barrier protection (protective equipment) for caregivers (mask, gown, goggles, and gloves) is very important to prevent other people from being infected.
  • Researchers are trying to understand the Ebola virus and pinpoint its ecological reservoirs to deduce how Ebola outbreaks occur. Researchers are actively trying to establish an effective vaccine against Ebola viruses with some success.

What is the history of Ebola hemorrhagic fever?

Picture of the Ebola virus, viewed with an electron microscope; SOURCE: CDC/Frederick Murphy

Ebola hemorrhagic fever first appeared in Zaire (currently, the Democratic Republic of the Congo or DRC or Congo) in 1976. The original outbreak was in a village named Fukuyama near the Ebola River after which the disease was named. During that time, researchers identified the virus in person-to-person contact transmission. Of the 318 patients diagnosed with Ebola, 88% died. The second outbreak occurred in Nzara, South Sudan, in 1976, with 151 deaths.

Since that time, there have been multiple outbreaks of Ebola virus, and researchers have identified five strains; four of the strains are responsible for the high death rates. The four Ebola strains are termed as follows: Zaire, Sudan, Tia Forest, and Burgundian virus, with Zaire Ebola virus being the most lethal strain. Researchers have found a fifth strain termed Res ton in the Philippines. The strain infects primates, pigs, and humans and causes few if any symptoms and no deaths in humans. Most outbreaks of the more lethal strains of Ebola have occurred in sub-Saharan West Africa and mainly in small- or medium-sized towns. Health care professionals believe bats, monkeys, and other animals maintain the non-human virus life cycle in the wild; humans can become infected from handling and/or eating infected animals.

Once an Ebola outbreak is recognized, African officials isolate the area until the outbreak ceases. However, in the outbreak that began in West Africa in March 2014, some of the infected people reached larger city centers before the outbreak was recognized; this caused further spread. The infecting Ebola virus detected during this outbreak was the Zaire strain, the most pathogenic strain of Ebola. Health agencies are terming this outbreak as an “unprecedented epidemic.” This epidemic spread quickly in the West African countries of Guinea and Sierra Leone. In addition, countries of Liberia, Nigeria, Senegal, Uganda, and Mali all reported confirmed infections with Ebola. In addition, a few infections or flare-ups of Ebola virus infection appeared in the United States, Spain, and the United Kingdom (see for example, the case of Pauline Caffeine, a nurse who became infected); most of the people with Ebola in these countries either were imported infections from West Africa or were newly spread infections from treating patients who originally became infected in Africa. Another outbreak occurred in the DRC in May 2018 in Biko, a small town 80 miles from Bandanna, with 46 reported infections and 26 deaths. Unfortunately, the large city of Bandanna, with over 1 million people, has recorded at least three people with Ebola. The DRC hopes to isolate or stop the spread of Ebola in the two areas by vaccinating anyone who may have had some physical contact with an infected person with a new chimeric virus vaccine that in 2015 showed good results in Ebola-infected patients.

Health officials now report over 1,000 deaths due to Ebola in areas like Butte in the Congo (DRC) and neighboring countries in an ongoing outbreak over the last 9 months. This outbreak is difficult to control because it is happening in a war zone where cooperation between countries to control the outbreak is uncoordinated and even considered unwelcome.

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