Ebola Virus Disease (EVD) is a rare and deadly disease most commonly affecting people and nonhuman primates (monkeys, gorillas, chimpanzees).
There are six known species of viruses within the genus Ebolavirus: Ebola virus (Zaire ebolavirus), Sudan virus (Sudan ebolavirus), Taï Forest virus (Taï Forest ebolavirus, formerly Cote d’Ivoire ebolavirus), Bundibugyo virus (Bundibugyo ebolavirus), Reston virus (Reston ebolavirus,) and Bombali virus (Bombali ebolavirus). Of these, only four are known to cause disease in people (Ebola, Sudan, Taï Forest, and Bundibugyo viruses). 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 the Congo. Since then, outbreaks have occurred sporadically in Africa. The natural reservoir host of Ebola viruses remains unknown. However, based on the nature of similar viruses, experts think the virus is animal-borne, with bats being the most likely reservoir.
Transmission
How the virus first infects a person at the start of an outbreak is not known. However, experts think the first patient becomes infected through contact with an infected animal such as a fruit bat or nonhuman primate.
People can be infected with the Ebola virus through direct contact (like touching) with:
- Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, semen) of a person who is sick with or has died from EVD
- Objects (such as clothes, bedding, needles, and syringes) contaminated with body fluids from a person sick with EVD or a body of a person who died from EVD
- Blood or body fluids of infected fruit bats or nonhuman primates such as apes and monkeys
- Semen from a man who recovered from EVD (through oral, vaginal, or anal sex)
Ebola virus CANNOT spread to others when a person has no signs or symptoms of EVD. Additionally, the virus is not spread through the air, by water, or in general, by food. However, in certain parts of the world, Ebola virus may spread through the handling and consumption of bushmeat (wild animals hunted for food). There is no evidence that mosquitos or other insects can transmit Ebola virus.
Signs and Symptoms
Symptoms of EVD may appear 2 to 21 days after exposure to the virus, but the average is 8 to 10 days. A person infected with Ebola virus is not contagious until symptoms appear. Signs and symptoms of EVD include:
- Fever
- Severe headache
- Fatigue
- Muscle pain
- Weakness
- Diarrhea
- Vomiting
- Stomach pain
- Unexplained bleeding or bruising
Risk of Exposure
Healthcare providers, family, and friends in close contact with EVD patients are at the highest risk of getting sick with EVD because they may be exposed to infected blood and body fluids. During an outbreak, EVD can spread quickly within healthcare settings. Infection control measures, like screening patients for signs/symptoms of EVD and practicing proper personal protective equipment procedures, must be in place to ensure exposure to Ebola virus does not occur.
Ebola viruses are found in several countries. Past EVD outbreaks have occurred in the following countries:
- Democratic Republic of the Congo (DRC)
- Gabon
- Guinea
- Ivory Coast
- Liberia
- Republic of the Congo (ROC)
- Sierra Leone
- Sudan
- Uganda
