Ebola virus disease (EVD) is a severe, often deadly illness caused by the Ebola virus. It can cause large outbreaks, epidemics, and pandemics with a devastating global impact on healthcare, economy, and society. The case-fatality rate has varied from 25% to 90% in past outbreaks, with an average mortality rate now reduced to approximately 50% due to heightened awareness, increased education, and early detection.
Etiology and Epidemiology
Ebola viruses, named after the Ebola River, emerged in 1976. They belong to the Filoviridae family, which also includes Marburgvirus and Cuevavirus. The 5 subtypes of Ebola virus that cause clinical disease in humans are Zaire (EBOV), Bundibugyo (BDBV), Sudan (SUDV), Tai Forest (TAFV), and Bombali (BOMV). Ebola virus (species Zaire ebolavirus) has caused the most outbreaks and is the most studied type.
Ebola viruses appear episodically in animal populations in regions close to the African equator. The natural reservoir is thought to be fruit bats of the Pteropodidae family. Since its discovery, over 25 EVD outbreaks have occurred, many confined to rural areas in Sudan, the Democratic Republic of Congo, Gabon, the Republic of the Congo, and Uganda. The largest epidemic occurred in Western Africa from late 2013 to 2016, with cases also found in parts of Europe and the United States.
Transmission of Ebola Virus
Ebola viruses are transmitted through direct contact with the body fluids of infected animals (spillover event) or humans. Body fluids include blood, saliva, urine, feces, sweat, breast milk, and semen. Transmission can also occur through contact with surfaces, objects, or medical devices contaminated with these fluids. Eating the meat of infected animals is another potential route of infection.
Ebola can be transmitted through sexual intercourse, involving the semen of an infected person. Anal, oral, and vaginal sexual intercourse can all transmit the virus. However, there is no evidence that Ebola can transfer through the vaginal fluids of an infected person.
It is very unlikely that Ebola is an airborne infection. Airborne infections spread through small respiratory droplets that hang in the air after coughing, heavy breathing, laughing, or sneezing. Ebola is not thought to spread this way.
Incubation Period and Symptoms
The incubation period for Ebola symptoms can range from 2 to 21 days after exposure, with most people experiencing symptoms 6 to 12 days after exposure. Initial signs and symptoms are often nonspecific and may include:
- Abrupt onset of fever or subjective fever
- Chills
- Myalgia (muscle pain)
- Fatigue
- Headache
- Sore throat
These initial symptoms can be similar to those of other common diseases like malaria, making early diagnosis challenging.
Progression of Symptoms
Four to five days after symptom onset, patients can progress to gastrointestinal symptoms, often referred to as "wet" symptoms. These can include:
- Severe watery diarrhea
- Nausea
- Vomiting
- Abdominal pain
Other symptoms that may develop include:
- Chest pain
- Shortness of breath
- Confusion
- Eye irritation and redness
- Hiccups
- Seizures
- Cerebral edema (swelling of the brain)
A maculopapular rash is sometimes noted. Bleeding is not universally present but can manifest later in the course of the disease. This bleeding can appear as petechiae (small red or purple spots), ecchymosis (bruising), oozing from venipuncture sites, mucosal hemorrhage, or blood in stool or vomitus. Unexplained bleeding is reported in about 40% of patients.
Pregnant women may experience spontaneous miscarriages. Patients with fatal disease typically develop more severe clinical signs early and die between days 6 and 16 from complications such as multiorgan failure and septic shock.
What we know (and don't know) about Ebola - Alex Gendler
Diagnosis of Ebola Virus Disease
Early and accurate diagnosis of Ebola is critical for infection control. However, because early symptoms are similar to those of other common diseases, diagnosis can be difficult. If a person has symptoms of Ebola and has been in an area where the virus is known to exist, they should be immediately isolated.
Diagnosis typically involves:
- Medical History: Asking about recent travel, potential exposures, and symptom onset.
- Physical Examination: Assessing vital signs, hydration status, and signs of bleeding or other complications.
- Laboratory Tests:
- Complete blood count (CBC): To evaluate hemoglobin, platelet, and leukocyte counts.
- Molecular testing (RT-PCR): To detect the presence of viral genetic material. These tests require specialized facilities (biosafety level 4).
- Rapid lateral flow assays: Quicker tests with varying sensitivity and specificity, useful in resource-limited settings.
- Serologic tests: To detect antibodies produced in response to the virus.
- Blood, urine, and other tests: To monitor organ function and check for signs of the virus.
Treatment and Supportive Care
The standard treatment for Ebola remains supportive therapy. This involves helping the body fight the disease by managing severe illness and its complications. Most people with Ebola need care in a hospital or well-equipped medical center.
Supportive care may include:
- Intravenous fluids to manage dehydration and electrolyte imbalances.
- Medications to manage symptoms and complications.
- Blood transfusions if severe anemia occurs.
Some specific therapies, such as monoclonal antibodies, are available for certain strains of the virus, like the Ebola Zaire strain. Experimental treatments may also be used in rare cases.
Patients are isolated during treatment to prevent the spread of the disease. Proper Infection Prevention and Control (IPC) measures, including the use of personal protective equipment (PPE), are paramount.
Complications and Long-Term Effects
Ebola is a severe disease that can lead to multiorgan system failure, shock, and death. Patients with fatal disease often die between days 6 and 16 of illness.
Even after recovery, individuals may experience long-term complications, including:
- Hepatitis (liver inflammation)
- Encephalitis (brain inflammation)
- Uveitis (eye inflammation)
- Spinal cord injury
- Body aches and weakness for weeks or months
Ebola virus can persist in body fluids for prolonged periods. For example, it has been found in semen for up to three months after recovery, and individuals should use condoms or abstain from sex during this period. Once someone recovers from Ebola, they develop antibodies that may last for at least 10 years, possibly longer, and they can no longer spread the virus through their blood.
Prevention of Ebola
Prevention is essential to reduce the risk of Ebola epidemics. Key prevention strategies include:
- Vaccination: A vaccine for some types of Ebola has been approved and is offered to individuals at risk of exposure.
- Avoiding Outbreaks: Staying away from areas with known outbreaks.
- Safe Practices: Avoiding contact with infected people or animals, washing hands often, and not touching or eating wild animals.
- Personal Protective Equipment (PPE): Healthcare workers and individuals caring for Ebola patients must wear head-to-toe protective gear with no skin exposed.
- Disinfection: Contaminated surfaces and gear need to be properly disinfected. Hospital-grade disinfectants, such as household bleach, can kill the virus.
- Safe Funeral Practices: Traditional funeral rites that involve touching the body of the deceased can contribute to the spread of the disease and should be modified.
If you travel to affected countries or suspect exposure, contact a health care provider immediately and inform them of your travel history and any potential exposures before going to a medical facility. Early recognition and prompt reporting to Public Health authorities are vital for contact tracing, surveillance, and controlling the spread of the disease.