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    Infectious Disease Prevention Section
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Ebola

Data   Investigation   Reporting   Resources

Organism, Causative agent, Etiologic agent
The infectious agent of Ebola Virus Disease (EVD) are viruses in the genus Ebolavirus, which is in the virus family Filoviridae. There are six identified Ebola virus species, four of which cause disease in humans: Zaire ebolavirus, Sudan ebolavirus, Taï Forest ebolavirus, and Bundibugyo ebolavirus.

Transmission
Ebola has been found in certain mammals (primates, bats) in Africa. It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts. The virus spills over from its reservoir hosts to people through direct contact with blood, other body fluids, or tissues of infected animals with bats or non-human primates being the most likely sources. Infected animals carrying the virus can transmit it to other animals, like apes, monkeys, duikers and humans.

Exposure occurs when a person touches infected body fluids or objects that are contaminated with them. The virus can get into the body through broken skin or mucous membranes in the eyes, nose, or mouth. Once infection occurs in a human, there are several ways it can spread to other people in direct contact. Ebola is spread through direct contact with:

  • A person who is sick or has died from EVD if the exposure was to blood or body fluids (including urine, saliva, sweat, feces, vomit, breast milk, semen)
  • Objects contaminated with the virus (e.g., surfaces, bedding, needles, syringes)
  • A male EVD survivor if the contact involves semen through oral, vaginal or anal sex

The risk of transmission is highest during the late stages of the illness, when the infected person has very high levels of the virus in their body and is vomiting, having diarrhea, or hemorrhaging. Risk of transmission is also high at the time of death if unprotected contact with deceased's body occurs. Post-mortem transmission has been linked to the preparation of the body for burial and during burial rituals or funeral services.

The Ebola virus CANNOT spread to others when a person shows no signs or symptoms of EVD. It is not typically transmitted by food, except through handling or consumption of infected wild animals hunted for food. EVD is not spread through airborne transmission.

Symptoms
EVD is a severe acute illness, usually with sudden onset of fever, fatigue, malaise, muscle pain, severe headache, sore throat, vomiting, diarrhea, abdominal pain, rash, symptoms of impaired liver or kidney function, bruising and bleeding. Symptoms may appear anywhere from 2 to 21 days after contact with the virus, with an average of 8 to 10 days. Many common illnesses can have these same symptoms, including influenza (flu) or malaria. 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

Prevention
In the United States, EVD is a very rare disease. In other parts of the world, especially in sub-Saharan Africa, Ebola virus is endemic and results in outbreaks.

When living in or traveling to a region where Ebola virus outbreaks occur, there are several ways to protect yourself and prevent the spread of EVD. Practicing good hand hygiene is an effective method in preventing the spread of dangerous germs, like the Ebola virus. Proper hand hygiene means washing hands often with soap and water or an alcohol-based hand sanitizer.

While in an area affected by Ebola, it is important to avoid the following:

  • Contact with blood and body fluids (such as urine, feces, saliva, sweat, vomit, breast milk, semen, and vaginal fluids).
  • 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 or blood, fluids and raw meat prepared from these animals (bushmeat) or meat from an unknown source.
  • Contact with semen from a man who had EVD until you know the virus is gone from the semen.

These same prevention methods apply when living in or traveling to an area affected by an ongoing 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.

The U.S. Food and Drug Administration (FDA) approved the Ebola vaccine rVSV-ZEBOV (called Ervebo®) on December 19, 2019. This is the first FDA-approved vaccine for Ebola.

This vaccine is given as a single dose vaccine and has been found to be safe and protective against Zaire ebolavirus, which has caused the largest and most deadly Ebola outbreaks to date.

On February 26, 2020, the Advisory Committee on Immunization Practices (ACIP) recommended pre-exposure prophylaxis vaccination with rVSV-ZEBOV for adults ≥ 18 years of age in the U.S. population who are at potential occupational risk of exposure to Zaire ebolavirus. This recommendation includes adults who are

  • Responding or planning to respond to an outbreak of EVD;
  • Laboratorians or other staff working at biosafety-level 4 facilities that work with live Ebola virus in the United States; or
  • Healthcare personnel working at federally designated Ebola Treatment Centers in the United States.

For healthcare providers looking for information about the Ebola vaccine and vaccinating ACIP recommended groups, visit Ebola Vaccine: Information about Ervebo®.

A two-dose vaccine regimen of a different vaccine that was also designed to protect against the Zaire ebolavirus species of Ebola was used under a research protocol in 2019 during an Ebola outbreak in the Democratic Republic of the Congo. The two doses of this vaccine use two different vaccine components (Ad26.ZEBOV and MVA-BN-Filo) and the regimen requires an initial dose and a “booster” dose 56 days later. This vaccine has not yet been approved by the FDA for routine use.

Texas Trends
In 2014, there were three cases of Ebola reported in Texas that were associated with the 2014-2016 West Africa Ebola Epidemic. The initial case was the first travel associated case of EVD diagnosed in the United States. Two nurses who cared for the sick Ebola patient (initial case) contracted EVD, marking the first known transmission of EVD in the United States. The patient died, and both nurses recovered. Since then, Texas public health engages in public health follow-up for persons with potential Ebola virus exposure involving risk assessment and management, most notably in 2021.
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Last updated October 10, 2022