Ebola disease is caused by infection with a group of viruses belonging to the genus Orthoebolavirus within the family Filoviridae.
The Pathogen
Ebola is caused specifically by four members of the Orthoebolavirus genus that infect humans:
Ebola virus (Zaire ebolavirus) – The most common and lethal species.
Sudan virus (Sudan ebolavirus)
Taï Forest virus (Taï Forest ebolavirus)
Bundibugyo virus (Bundibugyo ebolavirus)
(Note: Reston virus and Bombali virus also belong to this genus, but they are not known to cause severe disease or death in humans.)
Initial Spillover (Animal-to-Human Transmission)
The virus originates in wildlife before jumping to human populations. Fruit bats (family Pteropodidae) are considered the natural reservoir host.
Direct Contact with Reservoir Hosts: Humans contract the virus through contact with blood, secretions, organs, or bodily fluids of infected fruit bats.
Handling Bushmeat: Exposure or consumption of infected forest animals, such as non-human primates (monkeys, chimpanzees, gorillas), forest antelopes, or porcupines found ill or dead in the rainforest.
Human-to-Human Transmission
Once a person is infected, Ebola spreads rapidly through close personal contact. The virus is not transmitted through casual air contact like influenza or COVID-19.
Direct Body Fluid Contact: Entry of infected bodily fluids—such as blood, saliva, vomit, urine, feces, sweat, semen, or breast milk—through broken skin or mucous membranes (eyes, nose, mouth).
Contaminated Surfaces (Fomites): Touching objects, clothing, bedding, or medical equipment contaminated with fluids from an infected person.
Burial Practices: Handling or preparing the body of someone who died from Ebola, as viral loads remain exceptionally high after death.
Sexual Transmission: The virus can persist in certain body fluids, particularly semen, long after recovery.
