EBOLA DISEASE SYMPTOMS, TRANSMISSION, PREVENTION AND TREATMENT
What is Ebola Virus Disease?
Ebola virus disease (EVD) is a deadly disease with occasional outbreaks that occur mostly on the African continent. EVD most commonly affects people and nonhuman primates (such as monkeys, gorillas, and chimpanzees).
It is caused by an infection with a group of viruses within the genus Ebolavirus:
i. Ebola virus (species Zaire ebolavirus)
ii. Sudan virus (species Sudan ebolavirus)
iii. Taï Forest virus (species Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus)
iv. Bundibugyo virus (species Bundibugyo ebolavirus)
v. Reston virus (species Reston ebolavirus)
vi. Bombali virus (species Bombali ebolavirus)
Ebola virus disease (EVD), one of the deadliest viral diseases, was discovered in 1976 when two consecutive outbreaks of fatal hemorrhagic fever occurred in different parts of Central Africa.
The first outbreak occurred in the Democratic Republic of Congo (formerly Zaire) in a village near the Ebola River, which gave the virus its name. The second outbreak occurred in what is now South Sudan, approximately 500 miles (850 km) away.
Scientists later discovered that these outbreaks were caused by two genetically distinct viruses: Zaire ebolavirus and Sudan ebolavirus. They have since discovered four further ebolaviruses, two of which can cause human disease (four in total).
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:
ii. Aches and pains, such as severe headache and muscle and joint pain
iii. Weakness and fatigue
iv. Sore throat
v. Loss of appetite
vi. Gastrointestinal symptoms including abdominal pain, diarrhea, and vomiting
vii. 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.
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.
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:
1. Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, amniotic fluid, and semen) of a person who is sick with or has died from Ebola virus disease (EVD).
2. 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.
3. Infected fruit bats or nonhuman primates (such as apes and monkeys).
4. 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. There is no evidence that Ebola can be spread through sex or other contact with vaginal fluids from a woman who has had Ebola.
Body fluids that can transmit Ebola include:
- Breast milk
- Vaginal fluids
- Pregnancy-related fluids
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.
Prevention and Vaccine
Ebola virus disease (EVD) is a very rare disease that can cause illness in people. It is believed to occur naturally in specific animal populations that live in multiple sub-Saharan African countries.
In the areas where EVD is most common, Ebola virus is believed to spread at low rates among certain animal populations. Occasionally people become sick with Ebola after coming into contact with infected animals, which can lead to Ebola outbreaks in people who come in contact with them or others who have EVD.
When living in or traveling to a region where Ebola virus is potentially present, there are a number of ways to protect yourself and prevent the spread of EVD.
1. Avoid contact with blood and body fluids (such as urine, feces, saliva, sweat, vomit, breast milk, amniotic fluid, semen, and vaginal fluids) of people who are sick.
2. Avoid contact with semen from a man who has recovered from EVD, until testing shows that the virus is gone from his semen.
3. Avoid contact with items that may have come in contact with an infected person’s blood or body fluids (such as clothes, bedding, needles, and medical equipment).
4. Avoid funeral or burial practices that involve touching the body of someone who died from EVD or suspect EVD.
5. Avoid contact with bats, forest antelopes, and nonhuman primates (such as monkeys and chimpanzees) blood, fluids, or raw meat prepared from these or unknown animals (bushmeat).
These same prevention methods should be used when living in or traveling to an area experiencing an Ebola outbreak. After returning from an area experiencing an Ebola outbreak, people should monitor their health for 21 days and seek medical care immediately if they 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 [PDF – 1 MB] in the United States.
There are currently two treatments* approved by the U.S. Food and Drug Administration (FDA) to treat EVD caused by the Ebola virus, species Zaire ebolavirus, in adults and children.
The first drug approved in October 2020, Inmazeb™external icon, is a combination of three monoclonal antibodies. The second drug, Ebanga™external icon, is a single monoclonal antibody and was approved in December 2020.
Monoclonal antibodies (often abbreviated as mAbs) are proteins produced in a lab or other manufacturing facility that act like natural antibodies to stop a germ such as a virus from replicating after it has infected a person.
These particular mAbs bind to a portion of the Ebola virus’s surface called the glycoprotein, which prevents the virus from entering a person’s cells.
Both of these treatments, along with two others, were evaluated in a randomized controlled trial during the 2018-2020 Ebola outbreak in the Democratic Republic of the Congo.
Overall survival was much higher for patients receiving either of the two treatments that are now approved by the FDA. Neither Inmazeb™ nor Ebanga™ have been evaluated for efficacy against species other than Zaire ebolavirus.
Whether or not other treatments are available, basic interventions can significantly improve chances of survival when provided early. These are referred to as supportive care, and include:
i. Providing fluids and electrolytes (body salts) orally or through infusion into the vein (intravenously).
ii. Using medication to support blood pressure, reduce vomiting and diarrhea, and to manage fever and pain.
iii. Treating other infections, if they occur.
Disclaimer: The mention of any product names or non-United States Government entities on CDC Ebola websites is not meant to serve as an official endorsement of any such product or entity by the CDC, the Department of Health and Human Service, or the United States Government.
<> Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a rare but severe, often fatal illness in humans.
<> The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.
<> The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks.
<> Community engagement is key to successfully controlling outbreaks.
<> Good outbreak control relies on applying a package of interventions, namely case management, infection prevention and control practices, surveillance and contact tracing, a good laboratory service, safe and dignified burials and social mobilisation.
<> Vaccines to protect against Ebola have been developed and have been used to help control the spread of Ebola outbreaks in Guinea and in the Democratic Republic of the Congo (DRC).
<> Early supportive care with rehydration, symptomatic treatment improves survival. Two monoclonal antibodies (Inmazeb and Ebanga) were approved for the treatment of Zaire ebolavirus (Ebolavirus) infection in adults and children by the US Food and Drug Administration in late 2020.
<> Pregnant and breastfeeding women with Ebola should be offered early supportive care. Likewise vaccine prevention and experimental treatment should be offered under the same conditions as for non-pregnant population.