Ebola Disease

Ebola disease is a rare but severe illness caused by viruses that can lead to serious complications and death. While outbreaks primarily occur in parts of Africa, understanding how the disease spreads and recognizing symptoms early can save lives.

Table of contents

• What is Ebola disease
• Types of viruses that cause Ebola
• Signs and symptoms
• How Ebola spreads
• Who is most at risk
• Outbreak history
• Severity and mortality rates
• Treatment and supportive care
• Prevention measures
• Vaccination

What is Ebola disease

Ebola disease is caused by a group of viruses known as orthoebolaviruses, which are members of the filoviridae family. These viruses can cause serious illness that, without treatment, can lead to death.^[1] The disease is also known as Ebola virus disease or sometimes Ebola hemorrhagic fever, though the former name is now less commonly used.^[2]

Ebola hemorrhagic fever, Ebola virus disease, EVD

Ebola is a type of viral hemorrhagic fever, which means it is a viral infection that damages blood vessels and can cause bleeding. The disease is rare but can be life-threatening.^[3] Orthoebolaviruses were first discovered in 1976 in the Democratic Republic of the Congo and are found primarily in sub-Saharan Africa.^[1]

Types of viruses that cause Ebola

There are four orthoebolaviruses that cause illness in people. Each virus is named after the location where it was first identified, even if outbreaks have occurred in other places since then.^[1]

Ebola virus (species Orthoebolavirus zairense) causes Ebola virus disease. This is the most common cause of Ebola outbreaks and deaths.^[1] It is also known as the Zaire Ebola virus.^[5]

Sudan virus (species Orthoebolavirus sudanense) causes Sudan virus disease. This strain is more likely to be deadly.^[3]

Bundibugyo virus (species Orthoebolavirus bundibugyoense) causes Bundibugyo virus disease. This type is less likely to cause death than other strains.^[3]

Taï Forest virus (species Orthoebolavirus taiense) causes Taï Forest virus disease. This is the rarest cause of Ebola.^[3]

Two other orthoebolaviruses have been identified but do not cause illness in people. Reston virus can cause illness in nonhuman primates and pigs but not in humans. Bombali virus was identified in bats, but scientists do not yet know if it causes illness in animals or people.^[1]

Signs and symptoms

People with Ebola disease may experience symptoms in phases. Early in the illness, patients typically have what doctors call “dry” symptoms. These symptoms may include fever, aches, pains, and fatigue.^[1]

The first signs of Ebola can appear from 2 to 21 days after someone has been exposed to the virus. However, on average, symptoms begin 8 to 10 days after exposure.^[1]

Early symptoms often resemble the flu and include:^[3]

• Chills
• Feeling very tired (fatigue) and weak
• Fever
• Loss of appetite
• Muscle pain
• Severe headache
• Sore throat

As the person becomes sicker, the illness typically progresses to “wet” symptoms. Severe Ebola symptoms can develop a few days later and may include:^[1][3]

• Black, tarry stool (melena)
• Bleeding or bruising
• Confusion
• Diarrhea that may be bloody
• Rash or spots of blood under the skin
• Red or bloodshot eyes
• Vomiting that may be bloody or look like coffee grounds
• Unexplained bleeding

Later stages of Ebola can be severe and may include:^[3]

• Brain inflammation (encephalitis)
• Organ failure
• Seizures
• Shock (when the body does not get enough blood flow)

How Ebola spreads

It is thought that fruit bats of the Pteropodidae family are natural hosts of the orthoebolavirus. The virus can get into the human population when people have close contact with the blood, secretions, organs, or other bodily fluids of infected animals such as fruit bats, chimpanzees, gorillas, monkeys, forest antelope, or porcupines found ill or dead in the rainforest.^[2]

People can get Ebola disease through contact with the body fluids of an infected sick or dead person. Rarely, some people can get the disease from contact with an infected animal, like a bat or primate.^[1] Orthoebolaviruses spread through contact with body fluids of infected animals or humans. Body fluids include:^[3]

• Blood
• Urine
• Feces
• Saliva
• Sweat
• Vomit
• Breast milk
• Amniotic fluid
• Semen
• Vaginal fluid

You can get Ebola from surfaces, objects, or medical devices that come in contact with the virus. You may even get it from eating the meat of infected animals.^[3] The virus can spread through direct contact with contaminated materials such as bedding, clothes, needles, or medical equipment.^[1]

Ebola is not spread through the air, water, or food. It is also not spread by mosquitoes or other insects.^[6] Ebola can transfer through sexual intercourse that involves the semen of an infected person, including vaginal, oral, or anal sex.^[3]

People with Ebola disease do not spread the disease until they become sick. Infected people are safe to be with during the incubation period, which is the time between exposure and when a person gets symptoms.^[21] When living with or caring for someone with Ebola, the risk of transmission is highest when patients have a fever and feel sick. During the first few days of symptoms, the disease is not very contagious.^[16]

After someone recovers from Ebola, the virus can persist for several months in specific organs where the virus is shielded from the body’s immune system. These sites, called immunologically privileged sites, include the testes, interior of the eyes, placenta, and central nervous system.^[14] Semen from someone who has recovered from Ebola disease can contain the virus for at least 12 months.^[18]

Who is most at risk

Healthcare providers and family members caring for someone with Ebola disease without proper infection control methods have the highest risk of infection. The viruses that cause Ebola disease pose little risk to travelers or the general public.^[1]

Ebola outbreaks develop in countries of West, Central, and East Africa. Ebola viruses start in animals such as antelopes, fruit bats, and nonhuman primates like apes and monkeys.^[3] People are at risk of getting infected if they have direct contact with infected animals, consume their meat, or have close contact with sick individuals in outbreak areas.^[18]

Outbreak history

Ebola disease first occurred in 1976 in two simultaneous outbreaks. One outbreak was of Sudan virus disease in Nzara in what is now South Sudan, and the other outbreak was of Ebola virus disease in Yambuku, in what is now the Democratic Republic of the Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name.^[2]

Between 1979 and 1994, no human cases or outbreaks were detected. However, since 1994, outbreaks have been recognized with increasing frequency.^[5] Until 2014, outbreaks of Ebola disease were primarily reported from remote villages close to tropical rainforests in Central and West Africa. Most confirmed cases were reported from the Democratic Republic of the Congo, Gabon, the Republic of the Congo, Sudan, and Uganda.^[5]

The largest Ebola outbreak was between 2013 and 2016. In total, there were 28,652 cases worldwide, with 11,325 reported deaths in 10 countries.^[3] This outbreak, which began in February 2014 in Guinea, was the most prevalent Ebola outbreak recorded in history. It spread to Liberia, Sierra Leone, Nigeria, Senegal, Spain, and the United States.^[4] During this outbreak, there was intense transmission in urban areas.^[5]

More recent outbreaks have been confirmed in the Democratic Republic of the Congo between 2018 and 2020, Uganda between 2022 and 2023, and currently in the Democratic Republic of the Congo’s Kasai Province, which was declared in September 2025.^[20]

Severity and mortality rates

Orthoebolaviruses can cause serious and often deadly disease, with a mortality rate as high as 80 to 90 percent.^[1] The average Ebola disease case fatality rate is around 50 percent. Case fatality rates have varied from 25 to 90 percent in past outbreaks.^[2]

The mortality rate was around 90 percent when Ebola was first discovered in 1976. Although medical facilities have improved over the years, case fatality rates have varied from 25 to 90 percent in past outbreaks.^[4] Modern medicine and public health measures have been able to lower this figure and reduce the impact of the virus on individuals and communities.^[4]

Treatment and supportive care

Early intensive supportive care with rehydration and the treatment of symptoms improves survival. Seeking early care can be lifesaving.^[2] General medical support is critical and should include replacement of fluids and electrolytes. Such care must be administered with strict attention to barrier isolation.^[12]

Treatment involves early, aggressive supportive care with rehydration. Supportive therapy with attention to intravascular volume, electrolytes, nutrition, and comfort care is of benefit to the patient.^[12]

Approved vaccines and treatments are only available for one of the viruses, Ebola virus (Zaire ebolavirus), and are under development for the others.^[2] Two monoclonal antibodies, Ebanga and a cocktail of monoclonal antibodies called Inmazeb, received Food and Drug Administration approval in 2020.^[11]

The recombinant monoclonal antibody combination, atoltivimab/maftivimab/odesivimab (Inmazeb), was approved by the FDA in October 2020 and is the first approved treatment for Zaire ebolavirus. It is indicated for treatment of Zaire ebolavirus in adults and children, including neonates born to a mother who is positive for Zaire ebolavirus infection.^[12]

While there are licensed vaccines and therapeutics for Ebola virus disease, there is no approved vaccine or treatment for other Ebola diseases, such as Sudan virus disease or Bundibugyo virus disease. Candidate products are in development.^[2]

Prevention measures

When living in or traveling to regions where viruses that spread Ebola disease may be present, take steps to protect yourself.^[1]

Avoid contact with body fluids from people and animals, including:^[1]

• Blood and body fluids, like urine, feces, saliva, sweat, vomit, breast milk, amniotic fluid, semen, and vaginal fluid from people who are sick
• Semen from someone who has recovered from Ebola disease, until testing shows that the virus is no longer in the semen
• Clothes, bedding, needles, medical equipment, or other items that may have touched an infected person’s blood or body fluids
• The body of someone who is suspected or confirmed to have had Ebola disease (such as during a funeral or burial practices)
• Bats, forest antelopes, primates, and blood, fluids, or raw meat from these or unknown animals

Wash your hands frequently with soap and water. Use an alcohol-based hand sanitizer if soap and water are not available.^[18] Avoid all places and activities that could result in exposure. This includes places where sick people are being cared for without appropriate infection control measures.^[18]

Wear protective equipment if you come in contact with people who are sick or have died from Ebola disease, their blood and body fluids, or objects covered in body fluids.^[1] If you cannot avoid high-risk areas or activities, reduce your risk by taking proper precautions, such as wearing masks, gloves, gowns, and goggles.^[18]

Avoid sexual activity with anyone who is currently sick, including oral, vaginal, or anal sex. Avoid contact with semen from anyone who has recovered from Ebola disease until testing shows the virus is no longer present. If you have recovered from Ebola disease, you should avoid sexual contact for at least 12 months or use condoms correctly and consistently.^[18]

Avoid direct, unprotected contact with the body of a person who died of Ebola disease or an unknown illness. If you are taking part in burial practices, always maintain good personal hygiene and use proper personal protective equipment, like masks, gowns, gloves, and goggles.^[18]

Vaccination

There is an FDA-approved vaccine for the prevention of Ebola virus (species Orthoebolavirus zairense).^[1] The vaccine is called Ervebo (rVSV-ZEBOV), which is a recombinant vesicular stomatitis virus-vectored vaccine. It was the first vaccine to receive approval by the FDA in 2019.^[11]

This vaccine is genetically engineered to express a glycoprotein from Zaire ebolavirus to provoke a neutralizing immune response. It has shown an efficacy of 97.5 percent in preventing infection among 90,000 individuals in an active Ebola virus outbreak in the Democratic Republic of the Congo.^[12]

In a ring vaccination study conducted during the 2014 outbreak in the Republic of Guinea, results among the people who received the vaccine showed no Ebola cases were recorded 10 days or more after vaccination. In comparison, there were 23 cases 10 days or more after vaccination among those who did not receive the vaccine.^[12]

Multiple vaccines have been approved for Ebola disease prevention by various regulatory bodies. A safe and effective vaccine is an important tool to protect and prevent the introduction and spread of Ebola.^[12]