Ebola 

National Center for Emerging and Zoonotic Infectious Diseases

Division of High-Consequence Pathogens and Pathology (DHCPP)

Ebola, previously known as Ebola hemorrhagic fever, is a severe, often fatal disease in humans and nonhuman 

primates (such as monkeys, gorillas, and chimpanzees).

Ebola is a rare and deadly disease caused by infection with a virus of the family Filoviridae, genus Ebolavirus. There 

are five identified Ebolavirus species, four of which have caused disease in humans: Zaire ebolavirus; Sudan 

ebolavirus; Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus; and Bundibugyo ebolavirus. The fifth, Reston 

ebolavirus, has caused disease in nonhuman primates but not in humans.

Ebola is found in several African countries. The first Ebola species was discovered in 1976 near the Ebola River in 

what is now the Democratic Republic of the Congo. Since then, outbreaks have appeared sporadically in Africa.

The natural reservoir host of Ebola remains unknown. However, on the basis of available evidence and the nature of 

similar viruses, researchers believe that the virus is animal-borne with bats being the most likely reservoir. Four of the 

five subtypes occur in an animal host native to Africa.

Transmission

Because the natural reservoir host of Ebola has not yet been identified, the manner by which the virus first appears in 

a human at the start of an outbreak is unknown. However, researchers believe that the first patient becomes infected 

through contact with an infected animal.

When an infection does occur in humans, there are several ways the virus can be spread to others. These include:

• direct contact with the blood or body fluids (including but not limited to feces, saliva, urine, vomit and semen)

of a person who is sick with Ebola

• contact with objects (like needles and syringes) that have been contaminated with the blood or body fluids of 

an infected person or with infected animals

The virus in the blood and body fluids can enter another person’s body through broken skin or unprotected mucous 

membranes in, for example, the eyes, nose, or mouth. The viruses that cause Ebola are often spread among families 

and friends, because they come in close contact with blood or body fluids when caring for ill persons.

During outbreaks of Ebola, the disease can spread quickly within healthcare settings, such as clinics or hospitals. 

Exposure to Ebola can occur in healthcare settings where hospital staff are not wearing appropriate protective clothing 

including masks, gowns, gloves, and eye protection.

Dedicated medical equipment (preferably disposable, when possible) should be used by healthcare personnel 

providing care for someone sick with Ebola. Proper cleaning and disposal of instruments, such as needles and 

syringes, is also important. If instruments are not disposable, they must be sterilized before being used again. Without 

adequate instrument sterilization, virus transmission can continue and amplify an outbreak.

Signs and Symptoms

A person infected with Ebola is not contagious until symptoms appear.

Signs and Symptoms of Ebola typically include:

• Fever (greater than 38.6°C or 101.5°F)

• Severe headache

• Muscle pain

• Vomiting 

• Diarrhea

• Stomach pain

• Unexplained bleeding or bruising

Symptoms may appear anywhere from 2 to 21 days after exposure to Ebola but the average is 8 to 10 days.

Recovery from Ebola depends on the patient’s immune response. People who recover from Ebola infection develop 

antibodies that last for at least 10 years.
Risk of Exposure

Ebola is found in several African countries. Since 1976, Ebola outbreaks have occurred in the following countries:

• Democratic Republic of the Congo (DRC)

• Gabon

• South Sudan

• Ivory Coast

• Uganda

• Republic of the Congo (ROC)

• South Africa (imported) 

• Guinea

• Liberia

• Sierra Leone

• Senegal

• Nigeria

Because the natural reservoir host of Ebola, and the manner in which transmission of the virus to humans remain 

unknown, risk assessment in endemic areas is difficult. 

During outbreaks of Ebola, those at highest risk include healthcare workers and the family and friends of a person 

infected with Ebola. Healthcare workers in Africa should consult the Infection Control for Viral Hemorrhagic Fevers In 

the African Health Care Setting to learn how to prevent and control infections in these settings. Medical professionals 

in the United States should consult the Infection Prevention and Control Recommendations for Hospitalized Patients 

with Known or Suspected Ebola Hemorrhagic Fever in U.S. Hospitals.

Diagnosis

Diagnosing Ebola in a person who has been infected for only a few days is difficult because the early symptoms, such 

as fever, are not specific to Ebola infection and are seen often in patients with more commonly occurring diseases, 

such as malaria and typhoid fever.

However, if a person has symptoms of Ebola and had contact with blood or body fluids of a person sick with Ebola, 

contact with objects that have been contaminated with blood or body fluids of a person sick with Ebola or contact with 

infected animals, the patient should be isolated and public health professionals notified. Samples from the patient can 

then be collected and tested to confirm infection.

Laboratory tests used in diagnosis include

Timeline of Infection Diagnostic tests available

Within a few days after symptoms begin - Antigen-capture enzyme-linked immunosorbent assay 

(ELISA) testing

- IgM ELISA

- Polymerase chain reaction (PCR)

- Virus isolation

Later in disease course or after recovery - IgM and IgG antibodies

Retrospectively in deceased patients - Immunohistochemistry testing

- PCR

- Virus isolation
Treatment

Currently there are no specific vaccines or medicines (such as antiviral drug) that have been proven to be effective 

against Ebola.

Symptoms of Ebola are treated as they appear. The following basic interventions, when used early, can significantly 

improve the chances of survival:

• Providing intravenous(IV) fluids and balancing electrolytes (body salts)

• Maintaining oxygen status and blood pressure

• Treating other infections if they occur

Timely treatment of Ebola is important but challenging since the disease is difficult to diagnose clinically in the early 

stages of infection. Because early symptoms such as headache and fever are not specific to Ebolaviruses, cases of 

Ebola may be initially misdiagnosed.

However, if a person has symptoms of Ebola and had contact with blood or body fluids of a person sick with Ebola,

contact with objects that have been contaminated with blood or body fluids of a person sick with Ebola, or contact with 

an infected animal, the patient should be isolated and public health professionals notified. Supportive therapy can 

continue with proper protective clothing until samples from the patient are tested to confirm infection.

Experimental treatment has been tested and proven effective in some animals but has not yet been evaluated in 

humans.

Prevention

When cases of the disease do appear, there is increased risk of transmission within healthcare settings. Therefore, 

healthcare workers must be able to recognize a case of Ebola and be ready to use appropriate infection control 

measures. The aim of these techniques is to avoid contact with the blood or body fluids of an infected patient. 

Appropriate procedures include:

• isolation of patients with Ebola from contact with unprotected persons

• wearing of protective clothing (including masks, gloves, impermeable gowns, and goggles or face shields) by 

persons caring for Ebola patients

• the use of other infection-control measures (such as complete equipment sterilization and routine use of 

disinfectant)

• Avoid touching the bodies of patients who have died from Ebola

Healthcare workers should also have the capability to request diagnostic tests or prepare samples for shipping and 

testing elsewhere. 

CDC, in conjunction with the World Health Organization, has developed a set of guidelines to help prevent and control 

the spread of Ebola. Entitled Infection Control for Viral Hemorrhagic Fevers In the African Health Care Setting, the 

manual describes how to:

• recognize cases of viral hemorrhagic fever 

• prevent further transmission in health care setting by using locally available materials and minimal financial 

resources