Ebola is a rare, often deadly virus that causes a severe illness called hemorrhagic fever. Infection with the virus can damage blood vessels, affect multiple organs (e.g., kidneys, liver), and often leads to excessive bleeding (hemorrhage).
Ebola spreads through direct contact with the blood or body fluids of a person who has an Ebola infection or of someone who has died from it. A person is contagious only after symptoms appear. Contaminated objects such as needles can also transmit Ebola, as can contact with infected wildlife. Ebola enters the body through mucous membranes like the eyes and nose or broken skin. The virus does not spread through air, water, or casual contact with a carrier.
The Ebola virus incubates for about 8 to 10 days before moving to lymph nodes, then the liver, spleen and adrenal glands. Early Ebola symptoms are flu-like and similar to more common diseases like malaria and meningitis. Later symptoms become more severe and include unexplained bleeding and organ failure.
According to the World Health Organization (WHO), the Ebola fatality rate has ranged from 25% to 90%, depending on the outbreak.
In 1976, scientists first identified Ebola in what is now the Democratic Republic of the Congo. Since then, sub-Saharan Africa has been affected by periodic Ebola outbreaks. The West African outbreak that began in 2014 and ended in 2016 was the largest ever recorded, with 15,261 laboratory-confirmed cases, according to the WHO.
During that outbreak, ten people with Ebola were treated in the U.S. Two acquired it in the U.S. and the other cases were acquired in West Africa.
Since Ebola requires direct contact to spread from person-to-person, the risk of an outbreak in the U.S. is very low. Patients are not routinely tested for Ebola. A person may be tested if that person recently visited an area where the virus was reported and have symptoms, or if someone knows that he or she has been exposed to the virus and have symptoms consistent with an Ebola infection.
In addition to Ebola, other viruses causing hemorrhagic fever include Marburg, Hantavirus, and yellow fever. Many hemorrhagic fever viruses rely on an animal or insect host to survive. In the case of Ebola, these hosts are likely bats. Apes and monkeys can carry the virus too. Hemorrhagic fever outbreaks tend to be restricted to regions where those hosts live. Sometimes travelers carry the viruses outside the regions where the outbreak originated.
Early Ebola symptoms are usually non-specific and often similar to other infectious diseases that cause a high fever, and it can be difficult to distinguish between the diseases. If a healthcare practitioner suspects someone has a hemorrhagic fever, or a disease with similar symptoms, specific diagnostic tests will be used to identify the virus or bacteria.
Individuals being tested for the Ebola virus need to be isolated. Healthcare providers and anyone who may come into contact with the patient's blood and body fluids, including laboratory personnel, need to take extra safety precautions. Local and national public health officials are also notified if Ebola is suspected.