Ebola

Ebola refers to a group of diseases caused by orthoebolaviruses (previously known as ebolaviruses). Its symptoms usually start as “dry” and involve sudden fever, muscle pain, sore throat, and fatigue. These are often followed by “wet” symptoms like diarrhea, vomiting, and bleeding.  

According to the World Health Organization (WHO), the average Ebola fatality rate is around 50 percent. Death rates in past outbreaks have ranged from 25 percent to 90 percent, depending on the type of orthoebolavirus, medical response, and other circumstances.

The first Ebola outbreak occurred in 1976 along the Ebola River in the Democratic Republic of the Congo (previously known as Zaire). Shortly after, the second outbreak took place around 500 miles away in South Sudan. Experts determined that two separate orthoebolaviruses were responsible for the outbreaks. These are now called Orthoebolavirus zairense and Orthoebolavirus sudanense. More than 25 Ebola outbreaks have occurred since 1976, most of which have taken place in rural areas of Africa.

Many scientists believe African fruit bats are the source of orthoebolaviruses. These animals are therefore known as “reservoir hosts.” Infected bats can spread viruses to other animals such as antelopes, porcupines, monkeys, and apes. Humans can contract Ebola by touching an infected animal or its body fluids, or by preparing or eating its meat.

Ebola spreads from person to person through blood and body fluids, such as sweat, mucus, and saliva. It can also spread through direct contact with contaminated objects, such as medical equipment, towels, and clothes.

The largest Ebola outbreak in history took place in West Africa from 2014 to 2016. Some scientists believe it started in December 2013 when a young child in Guinea contacted an infected wild animal. Factors including traffic between countries, cultural practices that accelerated transmission, and the introduction of orthoebolavirus into crowded urban areas hastened the spread of the virus.  

The West Africa Ebola outbreak caused more than 28,600 infections and 11,325 deaths over the course of two and a half years. It largely affected Guinea, Sierra Leone, and Liberia, though cases were reported as far away as Spain, Italy, the United Kingdom, and the United States.

Most recently, Uganda experienced an Ebola outbreak that caused 164 infections and 55 deaths. The outbreak began in September 2022 and was declared over in January 2023.

Ebola infections in the United States  

Eleven people in the U.S. received treatment for Ebola during the 2014 West Africa outbreak. Many were medical workers who contracted Ebola while providing aid to people in Africa. In 2014, the first reported transmission of Ebola in the U.S. occurred in two nurses who were caring for a patient who traveled from West Africa to Dallas, Texas. Both nurses made full recoveries.

Overall, two people died of Ebola in the U.S. and nine recovered. No cases of Ebola have been diagnosed in the U.S. since 2014.

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Four orthoebolaviruses are known to cause different types of Ebola in humans. These include:

Ebola virus (Orthoebolavirus zairense): This is the most common and deadliest type of orthoebolavirus. It causes Ebola virus disease and was responsible for the West Africa outbreak in 2014.

Sudan virus (Orthoebolavirus sudanense): This causes Sudan virus disease, which has been involved in several outbreaks in Uganda and around the border of South Sudan and the Democratic Republic of the Congo. 

Bundibugyo virus (Orthoebolavirus bundibugyoense): This causes Bundibugyo virus disease, which has been involved in two outbreaks in Uganda and the Democratic Republic of the Congo.

Taï Forest virus (Orthoebolavirus taiense): This virus, formerly known as Côte d’Ivoire ebolavirus, causes Taï Forest virus disease, which has been linked to one case of Ebola on the Ivory Coast.

Two other types of orthoebolaviruses are known only to affect wild animals. Orthoebolavirus bombaliense has been found in bats but may not cause disease in humans or other animals. Orthoebolavirus restonense can cause Ebola in pigs and monkeys.

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Symptoms of Ebola can appear between two and 21 days after exposure to orthoebolavirus. On average, they occur eight to 10 days after infection. Ebola is usually only contagious when symptoms are present.

Ebola symptoms typically develop in stages. Early symptoms of Ebola may include:

• Fever
• Chills
• Muscle or joint pain
• Intense headache
• Sore throat
• Fatigue
• Weakness
• Hiccups  

As the disease progresses, symptoms can involve:

• Nausea and vomiting
• Chest pain
• Shortness of breath  
• Confusion
• Diarrhea
• Abdominal pain
• A painless skin rash that may be red or discolored and start to peel 
• Red eyes
• Unexplained bruising or bleeding
• Bleeding from the rectum, mouth, nose, or eyes

The final stage of Ebola may involve:  

• Seizures
• Inflammation in the brain
• Shock (poor blood flow in the body due to a drop in blood pressure) 
• Organ failure

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Call 911 if you’ve been exposed to Ebola or you’re experiencing symptoms and have recently traveled to affected parts of Africa (or have been around someone who has). Inform the 911 operator that you’ve been exposed to Ebola or are displaying possible symptoms.

Keep in mind that Ebola is a rare disease that hasn’t been seen in the U.S. since 2014. If you are in the U.S. and develop possible signs of Ebola, it’s more likely that you have another illness. More common conditions that share some symptoms with Ebola include:

• Influenza (the flu)
• Gastroenteritis (stomach flu)
• Typhoid fever
• Malaria    

Overall, it’s a good idea to speak with a healthcare provider (HCP) if you notice any changes in your health that concern you. Seek emergency medical care if you or someone around you experiences:

• Trouble breathing
• Chest pain
• Sudden dizziness or confusion
• Uncontrollable bleeding
• Loss of consciousness

If you develop a fever higher than 104 degrees Fahrenheit—or if your fever goes away but then returns—contact an HCP right away. (Infants younger than 12 weeks with a fever of any temperature should receive immediate medical attention.)

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Ebola is spread from an infected animal to a human in what’s known as a “spillover event.” This might involve hunting the animal or preparing or eating its meat. Some outbreaks have been linked to the consumption of contaminated monkey meat. Once introduced in the human population, Ebola spreads through unprotected direct contact with infected people or bodies. The disease becomes contagious once a person develops symptoms.

Human transmission of orthoebolavirus occurs through blood and body fluids, including:

• Sweat
• Saliva
• Mucus
• Urine
• Feces
• Vomit
• Breast milk 
• Amniotic fluid (the protective fluid that surrounds a fetus during pregnancy)
• Semen

Orthoebolavirus is also spread through objects contaminated with body fluids. These may include clothing, bed sheets, linens, door handles, toilets, toiletries, needles, and medical equipment. The virus can survive on surfaces for several hours and in most body fluids for days. Unprotected contact with infected bodies during funeral and burial practices has also contributed to Ebola outbreaks.

Research suggests that orthoebolavirus can survive in semen for extended periods of time. (There’s less evidence to suggest that orthoebolavirus can live or be transmitted through vaginal fluid.) It’s generally recommended to avoid unprotected sexual contact with a man or person assigned male at birth who has had Ebola for at least 12 months after the infection.

Unlike many other viral infections, Ebola generally isn’t transmissible through the air. There’s also no evidence to suggest that orthoebolaviruses are spread through mosquitos or other insects.

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Ebola outbreaks occur periodically in certain parts of Africa. If you live in the U.S., your risk of Ebola is very low.   

Traveling to Africa during an Ebola outbreak raises your risk of the disease, as does interacting with animals in certain parts of Africa (such as pigs, monkeys, fruit bats, antelope, and porcupines) that may carry orthoebolavirus. Animals in North America are not known to naturally carry orthoebolavirus.  

HCPs, humanitarian aid workers, and caregivers of people with Ebola have a high risk of contracting orthoebolavirus. Researchers who work with orthoebolavirus in laboratories are also at risk of infection.

Taking appropriate infection control measures (such as wearing personal protective equipment and using disposable medical supplies) can help prevent the spread of disease. People who reside in areas affected by Ebola should avoid contact with sick people or wear personal protective equipment if they’re near others with the disease.

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For an HCP to pursue a possible diagnosis of Ebola, a patient must have: 

• Symptoms that could indicate Ebola 
• Possible exposure to orthoebolavirus no more than 21 days before symptoms began 

A patient who meets these criteria should be isolated from others until an HCP can rule out Ebola and other dangerous infections.

Because the initial symptoms of Ebola are typically vague and often suggest more common conditions, identifying the disease early can sometimes be difficult. An HCP may begin by asking the patient about their recent travel history and if they’ve been in contact with others who are sick.

From there, several lab tests may be performed to screen for orthoebolavirus and other viruses and bacteria that could cause illness. This might include tests that evaluate samples of:

• Blood
• Urine
• Saliva
• Sputum (mucus coughed up from the lungs)
• Stool (feces or poop)

Performing a blood test is the most effective way to diagnose Ebola. Polymerase chain reaction (PCR) tests are the “gold standard” in Ebola testing, though they require special precautions and take several hours to perform. Other blood tests, including automated nucleic acid tests, are faster and easier to perform, though they’re not quite as accurate.

Blood tests that detect antibodies produced by a past or nearly resolved orthoebolavirus infection may also be used. Antibodies are blood proteins created by the immune system in response to a virus.

Public health officials will be notified if an individual is diagnosed with Ebola. These officials will take steps to limit the spread of infection and identify and monitor others who may have been exposed to the virus.

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Successful Ebola treatment begins with early supportive care. That means promptly treating symptoms (such as dehydration caused by vomiting or diarrhea) to increase a person’s chances of survival. All types of Ebola can be improved with supportive care.

Supportive care can include using medicines to:

• Stabilize blood pressure
• Help blood clot more effectively
• Manage fever and pain
• Relieve diarrhea and vomiting

Other supportive measures may include providing a patient with:

• Electrolytes and fluids given orally or through a vein in the arm (intravenously or IV) to address dehydration   
• Dialysis treatment to help filter toxins from blood
• Assisted ventilation or supplemental oxygen to maintain healthy oxygen levels in the body
• Care for other infections that may occur alongside Ebola

Less commonly, convalescent plasma therapy is used to treat Ebola. This therapy involves giving plasma (the liquid part of blood) from a person who has recovered from Ebola to a sick person through an IV in the arm. The plasma from the Ebola survivor contains orthoebolavirus antibodies that can help fight the disease and promote recovery.  

Throughout Ebola treatment, HCPs will check the patient’s blood pressure and other vital signs to monitor levels of the virus and screen for life-threatening symptoms, such as organ failure.

Medications to treat Ebola

In 2020, the U.S. Food and Drug Administration (FDA) approved two injection medications to treat Ebola caused by Orthoebolavirus zairense (the most common and deadly type) in children and adults. The first, Inmazeb (atoltivimab, maftivimab, and odesivimab-ebgn), is a drug with a combination of monoclonal antibodies. The second approved medication, Ebanga (ansuvimab-zykl), is a single monoclonal antibody drug.

Monoclonal antibodies are special proteins made in a laboratory. They work similarly to antibodies that are produced by the body in response to an infection. These drugs bind to a substance called glycoprotein found on the surface of the orthoebolavirus. In doing so, they help prevent orthoebolaviruses from reproducing and entering a person’s cells.  

The effectiveness of Inmazeb and Ebanga was evaluated during an Ebola outbreak that occurred in the Democratic Republic of the Congo from 2018 to 2020. Survival rates were significantly higher among people who received one of these drugs.

Inmazeb and Ebanga are only approved to treat Orthoebolavirus zairense. Additional monoclonal antibody drugs are currently being studied to treat other types of orthoebolaviruses.

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Many Ebola survivors face several years of complications following their recovery. A 2020 study published in Clinical Infectious Diseases found that two thirds of participants who recovered from Ebola experienced  their illness. These symptoms most often included a combination of headache, joint pain, and fatigue.

Some people who recover from Ebola develop vision issues, including blurry vision, increased sensitivity to light, excess tearing, eye pain, and eye floaters. Research also suggests that Ebola survivors have an increased risk of cataracts and uveitis (chronic eye inflammation). If left untreated, uveitis can lead to blindness.

Other widely reported long-term complications among Ebola survivors include muscle pain, weight gain, loss of appetite, and stomach pain.

Less commonly, Ebola complications may involve:

• Hair loss
• Dry mouth
• Memory loss  
• Hearing loss
• Ringing in the ears (tinnitus)
• Swelling of the tissue that surrounds the heart (pericarditis)
• Anxiety and depression
• Tingling sensations or pain in the hands or feet
• Testicle inflammation
• Trouble falling or staying asleep (insomnia)
• Erectile dysfunction  
• Loss of interest in sex
• Post-traumatic stress disorder (PTSD)

The severity, onset, and duration of Ebola complications appears to vary from person to person. There’s still more to learn about the complications of Ebola and how the disease affects survivors in the long term.  

Someone who has recovered from Ebola should speak with their HCP before breastfeeding or having sex, since the virus may remain in body fluids for some time following recovery.

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Ebola outbreaks can be prevented or contained with vaccination and proper infection control measures. Lessons learned from the 2014 West Africa outbreak have led to improved contact tracing and safer burial and funeral practices that maintain dignity for victims while minimizing the risk of virus transmission. Reliable lab services and increased education regarding how orthoebolaviruses spread from animals to people is also essential to preventing and minimizing outbreaks.

If you plan on visiting Africa or an area where Ebola outbreaks have previously occurred, be sure to follow these guidelines from the Centers for Disease Control and Prevention (CDC) to reduce your risk of contracting Ebola and to help prevent its spread:

• Avoid potentially infected animals (such as bats, monkeys, chimpanzees, and antelopes). This includes avoiding contact with their blood, body fluids, and meat.
• Avoid people who are sick. This includes avoiding contact with their blood and body fluids (such as saliva, sweat, urine, feces, vomit, and breast milk).
• Avoid items that are potentially contaminated with a sick person’s blood or body fluids (such as towels, clothing, bedding, and medical equipment).
• Avoid sexual contact with a man or person assigned male at birth who has recovered from Ebola until their semen has tested negative for orthoebolavirus.
• Avoid funeral and burial practices that involve direct contact with the body of someone who had or may have had Ebola. 

Additionally, wash your hands often and thoroughly with soap and water. Carry an alcohol-based hand sanitizer if you don’t have access to soap and water. If possible, try to avoid touching your mouth, eyes, or nose (or wash your hands before you do). Bandage or cover any scrapes, cuts, or sores you may have.

It’s also important to avoid traveling to areas that are experiencing an active Ebola outbreak. Before traveling internationally, check the CDC website for current Ebola outbreak and travel advisories. If you do visit an area affected by Ebola, carefully monitor your health for 21 days after you return and promptly report any possible Ebola symptoms to your HCP.

Is there a vaccine for Ebola?   

The FDA approved the first vaccine for Ebola in December 2019. Called Ervebo (rVSV-ZEBOV), this single-dose vaccine provides protection against the deadly Orthoebolavirus zairense in people 12 months of age and older.

A study published in the CDC’s Morbidity and Mortality Weekly Report that evaluated the effectiveness of Ervebo during the West Africa outbreak in 2015 showed that no participant in close contact with orthoebolavirus developed the disease for 10 or more days after being vaccinated. Another study, published in February 2024 in The Lancet Infectious Diseases, found that Ervebo vaccination can significantly lower the risk of death in sick people with an active Ebola infection.

Ervebo is approved for use in several African countries, including Guinea, the Democratic Republic of the Congo, Uganda, Burundi, Central African Republic, Ghana, Zambia, and Rwanda. Because Ebola outbreaks are still relatively uncommon and unpredictable in Africa, Ervebo vaccination is reserved as an outbreak response measure for people who are considered to have the highest risk of contracting the disease. Access to a global stockpile of the vaccine, managed by the International Coordinating Group on Vaccine Prevention, is made available as Ebola outbreaks occur.

Ervebo isn’t marketed to the general public in the U.S. But pre-exposure vaccination is made available to the following groups through the CDC:

• Frontline workers and responders during an Ebola outbreak caused by Orthoebolavirus zairense
• Lab technicians and support staff who handle live orthoebolavirus in laboratories
• HCPs at designated Ebola Treatment Centers and Special Pathogens Treatment Centers involved in the care of Ebola patients in the U.S.

The two-dose Zabdeno vaccine, which is not FDA approved but authorized for use in the European Union, also provides protection against Ebola caused by Orthoebolavirus zairense. It is available by prescription to people 12 months of age and older. Because doses of the Zabdeno vaccine are given eight weeks apart, the vaccine is used as a preventive measure and not during active outbreaks when immediate protection is necessary.

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Ebola is a dangerous infection that requires immediate treatment. If left untreated (or if treatment is ineffective), Ebola often results in death around 10 days after the start of symptoms.  

The average Ebola death rate is around 50 percent, though this figure can vary between 25 and 90 percent based on the type of orthoebolavirus, the medical response, and other factors. The death rate of untreated Ebola caused by Orthoebolavirus zairense is between 70 and 90 percent. Many survivors of Ebola also have complications such as joint pain and fatigue for several years after their illness.

Overall, the introduction of Ebola vaccines and monoclonal antibody medications is improving outcomes for people in affected areas. Additionally, those who recover from Ebola develop antibodies that may provide immunity from the disease for 10 years or longer. Researchers are unsure if this immunity applies to all types of orthoebolaviruses.

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Ebola is a rare and relatively new disease. Experts are continuing to discover more about Ebola, its causes, and how it can best be treated and prevented. To stay up to date on the latest Ebola news, visit the Centers for Disease Control and Prevention or World Health Organization website.

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• Lessons from the Largest Ebola Outbreak in History
• How Ebola Spreads  
• Ebola Timeline: Tracking a Deadly Virus