FAQs on Ebola (Signs and Symptoms, transmission and Laboratory diagnosis)

· Virology

What is Ebola?

Ebola, previously known as Ebola hemorrhagic fever, is a severe, most often fatal disease in humans and nonhuman primates. Ebola is a rare and deadly disease caused by infection with a virus of the family Filoviridae, genus Ebolavirus.  These are filamentous, enveloped particles with a single stranded RNA genome( approx. 19 kb long). There are five identified Ebolavirus subtypes , four of which have been associated with disease in humans:

  • Zaire ebolavirus
  • Sudan ebolavirus
  • Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus
  • Bundibugyo ebolavirus
  • Reston ebolavirus, has caused disease in nonhuman primates but not in humans.

Ebola is found in several African countries. The first Ebola species was discovered in 1976 near the Ebola River in what is now the Democratic Republic of the Congo. Since then, outbreaks have appeared sporadically in Africa. The natural reservoir host of Ebola remains unknown. However, on the basis of available evidence and the nature of similar viruses, researchers believe that the virus is animal-borne with bats being the most likely reservoir. Four of the five subtypes occur in an animal host native to Africa.


Because the natural reservoir host of Ebola has not yet been identified, the manner by which the virus first appears in a human at the start of an outbreak is unknown. However, researchers believe that the first patient becomes infected through contact with an infected animal.

When an infection does occur in humans, there are several ways the virus can be spread to others.

These include:

  • direct contact with the blood or body fluids (including but not limited to feces, saliva, urine, vomit and semen) of a person who is sick with Ebola
  • contact with objects (like needles and syringes) that have been contaminated with the blood or body fluids of an infected person or with infected animals

The virus in the blood and body fluids can enter another person’s body through broken skin or unprotected mucous membranes in, for example, the eyes, nose, or mouth. The viruses that cause Ebola are often spread among families and friends, because they come in close contact with blood or body fluids when caring for ill persons.

During outbreaks of Ebola, the disease can spread quickly within healthcare settings, such as clinics or hospitals. Exposure to Ebola can occur in healthcare settings where hospital staff are not wearing appropriate protective clothing including masks, gowns, gloves, and eye protection.

Dedicated medical equipment (preferably disposable, when possible) should be used by healthcare personnel providing care for someone sick with Ebola. Proper cleaning and disposal of instruments, such as needles and syringes, is also important. If instruments are not disposable, they must be sterilized before being used again. Without adequate instrument sterilization, virus transmission can continue and amplify an outbreak.

Signs and Symptoms of Ebola

A person infected with Ebolavirus is not contagious until symptoms appear.

Signs and Symptoms of Ebola typically include:

  • Fever (greater than 38.6°C or 101.5°F)
  • Severe headache
  • Muscle pain
  • Vomiting
  • Diarrhea
  • Stomach pain
  • Unexplained bleeding or bruising

Symptoms may appear anywhere from 2 to 21 days after exposure to Ebola but the average is 8 to 10 days.Recovery from Ebola depends on the patient’s immune response. People who recover from Ebola infection develop antibodies that last for at least 10 years.

Diagnosis of Ebola

Diagnosis of Ebola infection in a infected person is difficult for only a few days because the early symptoms, such as fever, are not specific to Ebola infection and are seen often in patients with more commonly occurring diseases, such as malaria and typhoid fever.

However, if a person has symptoms of Ebola and had contact with blood or body fluids of a person sick with Ebola, contact with objects that have been contaminated with blood or body fluids of a person sick with Ebola or contact with infected animals, the patient should be isolated and public health professionals notified. Samples from the patient can then be collected and tested to confirm infection.

Laboratory tests used in different timeline  for diagnosis include

  • Within a few days after symptoms begin
    • Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing
    • IgM ELISA
    • Polymerase chain reaction (PCR)
    • Virus isolation
  • Later in disease course or after recovery
    • IgM and IgG antibodies
  • Retrospectively in deceased patients
    • Immunohistochemistry testing
    • PCR
    • Virus isolation

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