Scientists think people are initially infected with Ebola virus through contact with an infected animal, such as a fruit bat or nonhuman primate. This is called a spillover event. After that, the virus spreads from person to person, potentially affecting a large number of people.
The virus spreads through direct contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with:
- Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, and semen) of a person who is sick with or has died from Ebola Virus Disease (EVD)
- Objects (such as needles and syringes) contaminated with body fluids from a person sick with EVD or the body of a person who died from EVD
- 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). The virus can remain in certain bodily fluids (including semen) of a patient who has recovered from EVD, even if they no longer have symptoms of severe illness.
When someone gets infected with Ebola, they will not show signs or symptoms of illness right away. The Ebola virus CANNOT spread to others until a person develops signs or symptoms of EVD. After a person infected with Ebola develops symptoms of illness, they can spread Ebola to others.
Additionally, Ebola virus usually is not transmitted 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 also no evidence that mosquitoes or other insects can transmit Ebola virus.
Persistence of the virus
There is no known risk of becoming infected with Ebola virus through casual contact with a survivor. However, the virus can remain in certain bodily fluids and continue to spread to others after a person has recovered from the infection. The virus can persist in semen, breast milk, ocular (eye) fluid, and spinal column fluid. Areas of the body that contain these fluids are known as immunologically privileged sites. These are sites of the body where viruses and pathogens, like Ebola virus, can remain undetected even after the immune system has cleared the virus from other sites of the body. Scientists are now studying how long the virus stays in these body fluids among Ebola survivors.
During an Ebola outbreak, the virus can spread quickly within healthcare settings (such as clinics or hospitals). Clinicians and other healthcare personnel providing care should use dedicated medical equipment, preferably disposable. Proper cleaning and disposal of instruments such as needles and syringes are important. If instruments are not disposable, they must be sterilized before additional use.
Ebola virus is killed using a U.S. Environmental Protection Agency (EPA)-registered hospital disinfectant pdf icon[PDF – 278KB]external icon with a label claim for a non-enveloped virus. On dry surfaces, like doorknobs and countertops, the virus can survive for several hours. However, in body fluids, like blood, the virus can survive up to several days at room temperature.
Pets and livestock
Serologic studies show that Ebola virus has been detected in dogs and cats found in Ebola affected areas, but there are no reports of dogs or cats becoming sick with EVD, or spreading the Ebola virus to people or other animals.1
Certain exotic or unusual pets (monkeys, apes, or pigs) have been known to be infected with Ebola virus. Pigs are the only species of livestock known to be at risk of infection by an Ebola virus. In the Philippines and China, pigs are naturally infected with Ebola Reston virus (Reston ebolavirus), which does not cause illness in people. In a laboratory setting, pigs have developed illness when infected with an extremely high dose of Zaire ebolavirus, but they are not known to be involved in the spread of this virus strain to humans.
 Allela L, Bourry O, Pouillot R. et al. Ebola Virus Antibody Prevalence in Dogs and Human Risk. Emerging Infectious Diseases. Vol. 11, No. 3, March 2005.