Ebola virus disease

• Ebola Virus Disease (EVD) is a rare and deadly disease in people and nonhuman primates.
• The viruses that cause EVD are located mainly in sub-Saharan Africa.
• People can get EVD through direct contact with an infected animal (bat or nonhuman primate) or a sick or dead person infected with Ebola virus.

Ebola virus

About Ebola virus

• To learn more about the virus causing Ebola virus disease, or Ebola hemorrhagic fever, see Ebola virus.

Transmission

• 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 clothes, bedding, needles, and medical equipment) contaminated with body fluids from a person who is sick with or has 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 body fluids (including semen) of a patient who has recovered from EVD, even if they no longer have symptoms of severe illness.

2014 ebola virus epidemic in West Africa simplified

Other methods of transmission

• There is no evidence that Ebola can be spread through sex or other contact with vaginal fluids from a woman who has had Ebola.

When people become infected with Ebola, they do not start developing signs or symptoms right away. This period between exposure to an illness and having symptoms is known as the incubation period. A person can only spread Ebola to other people after they develop signs and symptoms of Ebola.

• Additionally, Ebola virus is not known to be transmitted through food.
• However, in certain parts of the world, Ebola virus may spread through the handling and consumption of wild animal meat or hunted wild animals infected with Ebola.
• There is no evidence that mosquitoes or other insects can transmit Ebola virus.

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CDC 2016 Ebola Contact-tracing

Risk factors

• Health workers who do not use proper infection control while caring for Ebola patients, and family and friends in close contact with Ebola patients, are at the highest risk of getting sick.
• Ebola can spread when people come into contact with infected blood or body fluids.
• Ebola poses little risk to travelers or the general public who have not cared for or been in close contact (within 3 feet or 1 meter) with someone sick with Ebola.

Persistence of the virus

• The virus can remain in areas of the body that are immunologically privileged sites after acute infection.
• These are sites where viruses and pathogens, like the Ebola virus, are shielded from the survivor’s immune system, even after being cleared elsewhere in the body.
• These areas include the testes, interior of the eyes, placenta, and central nervous system, particularly the cerebrospinal fluid.
• Whether the virus is present in these body parts and for how long varies by survivor.
• 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).
• Ebola virus can survive on dry surfaces, like doorknobs and countertops for several hours; in body fluids like blood, the virus can survive up to several days at room temperature. Cleaning and disinfection should be performed using a hospital-grade disinfectant.

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Ebola-zaire chart

Signs and Symptoms

• Symptoms may appear anywhere from 2 to 21 days after contact with the virus, with an average of 8 to 10 days.
• The course of the illness typically progresses from “dry” symptoms initially (such as fever, aches and pains, and fatigue), and then progresses to “wet” symptoms (such as diarrhea and vomiting) as the person becomes sicker.

• Primary signs and symptoms of Ebola often include some or several of the following:

• Fever
• Aches and pains, such as severe headache, muscle and joint pain, and abdominal (stomach) pain
• Weakness and fatigue
• Gastrointestinal symptoms including diarrhea and vomiting
• Abdominal (stomach) pain
• Unexplained hemorrhaging, bleeding or bruising
• Other symptoms may include red eyes, skin rash, and hiccups (late stage).

• Many common illnesses can have the same symptoms as EVD, including influenza (flu), malaria, or typhoid fever.

Genomic epidemiology

• EVD is a rare but severe and often deadly disease. Recovery from EVD depends on good supportive clinical care and the patient’s immune response.
• Studies show that survivors of Ebola virus infection have antibodies (proteins made by the immune system that identify and neutralize invading viruses) that can be detected in the blood up to 10 years after recovery.
• Survivors are thought to have some protective immunity to the type of Ebola that sickened them.

Ebola vaccine Ervebo

• The U.S. Food and Drug Administration (FDA) has approved the Ebola vaccine rVSV-ZEBOV (tradename “Ervebo”) for the prevention of EVD. The rVSV-ZEBOV vaccine has been found to be safe and protective against only the Zaire ebolavirus species of ebolavirus.

Diagnosis

• Diagnosing Ebola virus disease (EVD) shortly after infection can be difficult. Early symptoms of EVD such as fever, headache, and weakness are not specific to Ebola virus infection and often are seen in patients with other more common diseases, like malaria and typhoid fever.

Ebola virus virion

• To determine whether EVD is a possible diagnosis, there must be a combination of symptoms suggestive of EVD AND a possible exposure to EVD within 21 days before the onset of symptoms. An exposure may include contact with:

• blood or body fluids from a person sick with or who died from EVD,
• objects contaminated with blood or body fluids of a person sick with or who died from EVD,
• infected fruit bats and nonhuman primates (apes or monkeys), or
• semen from a man who has recovered from EVD.
• If a person shows signs of EVD and has had a possible exposure, he or she should be isolated (separated from other people) and public health authorities notified. Blood samples from the patient should be collected and tested to confirm infection. Ebola virus can be detected in blood after onset of symptoms. It may take up to three days after symptoms start for the virus to reach detectable levels.

Ebola Pathenogensis path

• Polymerase chain reaction (PCR) is one of the most commonly used diagnostic methods because of its ability to detect low levels of Ebola virus. PCR methods can detect the presence of a few virus particles in small amounts of blood, but the ability to detect the virus increases as the amount of virus increases during an active infection. When the virus is no longer present in great enough numbers in a patient’s blood, PCR methods will no longer be effective. Other methods, based on the detection of antibodies an EVD case produces to an infection, can then be used to confirm a patient’s exposure and infection by Ebola virus.

• A positive laboratory test means that Ebola infection is confirmed. Public health authorities will conduct a public health investigation, including identifying and monitoring all possibly exposed contacts.

Prevention and Vaccine

• In the United States, Ebola virus disease (EVD) is a very rare disease that has only occurred because of cases that were acquired in other countries, eventually followed by person-to-person transmission. EVD is most common in parts of sub-Saharan Africa, with occasional outbreaks occurring in people. In these areas, Ebola virus is believed to circulate at low rates in certain animal populations (enzootic). Occasionally people become sick with Ebola after coming into contact with these infected animals, which can then lead to Ebola outbreaks where the virus spreads between people.

• When living in or traveling to a region where Ebola virus is present, there are a number of ways to protect yourself and prevent the spread of EVD

• Contact with blood and body fluids (such as urine, feces, saliva, sweat, vomit, breast milk, semen, and vaginal fluids) of persons who are ill.
• Contact with semen from a man who has recovered from EVD, until testing verifies the virus is gone from the semen.
• Items that may have come in contact with an infected person’s blood or body fluids (such as clothes, bedding, needles, and medical equipment).
• Funeral or burial rituals that require handling the body of someone who died from EVD.
• Contact with bats and nonhuman primates’ blood, fluids, or raw meat prepared from these animals (bushmeat).
• Contact with the raw meat of an unknown source.
• These same prevention methods apply when living in or traveling to an area affected by an Ebola outbreak. After returning from an area affected by Ebola, monitor your health for 21 days and seek medical care immediately if you develop symptoms of EVD.

Ebola Vaccine

• The U.S. Food and Drug Administration (FDA) approved the Ebola vaccine rVSV-ZEBOV (tradename “Ervebo”) on December 19, 2019. The rVSV-ZEBOV vaccine is a single dose vaccine regimen that has been found to be safe and protective against only the Zaire ebolavirus species of ebolavirus. This is the first FDA approval of a vaccine for Ebola.
• Another investigational vaccine was developed and introduced under a research protocol in 2019 to combat an Ebola outbreak in the Democratic Republic of the Congo. This vaccine leverages two different vaccine components (Ad26.ZEBOV and MVA-BN-Filo) and requires two doses with an initial dose followed by a second “booster” dose 56 days later. The second vaccine is also designed to protect against only the Zaire ebolavirus species of Ebola.

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