What is Ebola and how does it spread?

Ebola virus disease (EVD) or just Ebola, is a rare and deadly disease caused by infection with one of the Ebola virus species. The virus is transmitted to people from animals, and spreads in the human population through human-to-human transmission. Previously known as Ebola hemorrhagic fever, it was first detected in 1976 in Sudan and the Democratic Republic of Congo. Researchers named the disease after the Ebola river. Until recently, Ebola appeared in Africa only.

There are five strains of Ebola virus, which were named for the location where they were identified. These include:

  • Zaire
  • Sudan
  • Tai Forest
  • Bundibugyo
  • Reston

The Zaire ebolavirus is the most deadly to humans. The Reston ebolavirus is not known to cause disease in humans.

Causes of Ebola

Ebola is caused by infection with a virus of the Filoviridae and Ebolavirus family. These virus types cause hemorrhagic fever or profuse bleeding inside and outside the body. The Ebola virus is considered a zoonotic virus, meaning that the virus is present in animals and is transmitted to humans. Infected humans can transfer the virus others.

Transmission from animals to humans

Ebola is spread to humans through contact with an infected animal’s blood, bodily fluids or tissues. People who handle these infected animals have a chance of getting infected. The following animals can transmit the virus:

  • Chimpanzees
  • Forest antelopes
  • Gorillas
  • Monkeys
  • Porcupines
  • Fruit bats

Transmission from person to person

Infected people generally will not transmit the infection until they develop any symptoms. You can’t get Ebola from air, water, or food. The virus can only spread from individual to individual through direct contact with bodily fluids or secretions from infected people, such as:

  • Blood
  • Breast milk
  • Saliva
  • Semen
  • Sweat
  • Stool
  • Urine
  • Vomit

All these bodily fluids can carry the Ebola virus. Transmission can occur through eyes, nose, mouth, broken skin, or sexual contact. It can also occur through contact with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids. Doctors and medical personnel are especially at risk because they often deal with blood and bodily fluids. People remain infectious as long as their blood contains the virus.

Other infection risk factors include:

  • Exposure to infectious secretions when caring for an ill individual.
  • Exposure to contaminated needles or other surfaces.
  • Going to burial ceremonies in which mourners have direct contact with the body of someone who has died from Ebola.
  • Interacting with infected animals.
  • Travelling to areas where a recent outbreak has occurred.