Ebola virus disease (EVD), often referred to simply as Ebola, is a severe and frequently fatal illness that affects humans and other primates. Since its initial identification in 1976, outbreaks have occurred intermittently, primarily in tropical Africa. Understanding the origins of this virus is important for preventing future outbreaks and protecting public health.
The Primary Animal Reservoir
Fruit bats are the natural reservoir for Ebola viruses. These bats can carry the virus without developing symptoms. Evidence includes the detection of Ebola virus RNA and antibodies in several fruit bat species during outbreak investigations.
Specific species implicated include the hammer-headed fruit bat (Hypsignathus monstrosus), Franquet’s epauletted fruit bat (Epomops franqueti), and the straw-colored fruit bat (Eidolon helvum). The geographical distribution of these bat species aligns with regions where human Ebola outbreaks have occurred. Although the virus has been difficult to isolate from bats, the presence of viral genetic material and immune responses indicates their role as carriers.
How the Virus Spills Over to Humans
The transfer of Ebola virus from its animal reservoir to humans, known as a spillover event, occurs through direct contact with infected animals or their bodily fluids. This can happen when people engage in activities such as hunting, handling, or consuming bushmeat. Primates like chimpanzees and gorillas, and forest antelopes (duikers), can become infected by the virus through contact with bat droppings or contaminated fruit.
Humans can then contract the virus by coming into contact with the blood, organs, or other bodily fluids of these infected animals. These animals are intermediate hosts, meaning they contract the virus from the primary reservoir but are not long-term carriers. The virus can enter the human body through broken skin or mucous membranes in the eyes, nose, or mouth.
Reducing the Risk of Animal-to-Human Transmission
Minimizing the risk of Ebola transmission from animals involves adopting precautionary measures. Avoiding direct contact with wild animals, particularly those that appear sick or are found dead, reduces exposure. This includes refraining from touching or handling carcasses of wild animals.
When handling meat from wild animals, wear gloves and other protective clothing to prevent direct skin contact with blood or other bodily fluids. Thoroughly cooking all meat before consumption can help inactivate any potential viruses. Practicing good hygiene, such as washing hands with soap and water after any contact with animals or animal products, further reduces the risk of transmission.