Ebola Virus Disease: Symptoms, Causes & Treatment

What Is Ebola Virus Disease?

Ebola virus disease (EVD) is a severe, often fatal illness caused by the Ebola virus, a member of the Filoviridae family. The virus causes viral hemorrhagic fever with case fatality rates ranging from 25% to 90%. Ebola is a zoonotic disease, meaning it spreads from animals to humans, with fruit bats believed to be the natural reservoir.

Ebola virus disease was first identified in 1976 during two simultaneous outbreaks in what is now the Democratic Republic of the Congo (then Zaire) and in Sudan. The disease takes its name from the Ebola River in the DRC, near where the first outbreak occurred. Since then, there have been numerous outbreaks across Central and West Africa, with the largest occurring in West Africa from 2014 to 2016, affecting primarily Guinea, Liberia, and Sierra Leone.

The Ebola virus belongs to the family Filoviridae, which also includes the Marburg virus. There are six known species of Ebolavirus, four of which can cause disease in humans: Zaire ebolavirus (the most common and deadliest), Sudan ebolavirus, Bundibugyo ebolavirus, and Taï Forest ebolavirus. The Reston ebolavirus can infect humans but has not caused illness, while Bombali ebolavirus was discovered more recently in bats.

Understanding the epidemiology of Ebola is crucial for public health preparedness. The virus causes sporadic outbreaks primarily in remote regions of Central and West Africa, where healthcare infrastructure may be limited. Outbreaks often begin when a person comes into contact with an infected animal, such as a fruit bat or primate, and then spreads through human-to-human transmission in communities and healthcare settings.

How Ebola Affects the Body

When the Ebola virus enters the body, it targets cells of the immune system, including macrophages and dendritic cells. The virus replicates rapidly, releasing viral particles and triggering an overwhelming inflammatory response. This leads to widespread damage to blood vessels, impaired blood clotting, and multi-organ dysfunction.

The virus causes severe damage to the endothelial cells lining blood vessels, leading to increased vascular permeability. This results in fluid leakage, internal bleeding, and eventually shock. The immune system becomes dysregulated, leading to what scientists call a "cytokine storm" – an excessive inflammatory response that causes further tissue damage.

Why Is Ebola So Deadly?

Several factors contribute to Ebola's high mortality rate. The virus evades the immune system effectively, replicates rapidly, and causes severe systemic illness before the body can mount an adequate defense. The combination of vascular damage, coagulation problems, and organ failure can be fatal within days of symptom onset in severe cases.

What Are the Symptoms of Ebola?

Ebola symptoms typically appear 2-21 days after exposure and include sudden onset of fever, severe headache, muscle pain, fatigue, diarrhea, vomiting, and abdominal pain. In severe cases, internal and external bleeding may occur, though hemorrhaging is less common than previously believed, occurring in approximately 50% of cases.

The clinical presentation of Ebola virus disease progresses through distinct phases. Understanding these phases helps healthcare providers recognize the disease early and provide appropriate supportive care. The symptoms can be categorized into early, intermediate, and late stages, each with characteristic features that inform treatment decisions.

Early Symptoms (Days 1-3)

The initial symptoms of Ebola often mimic common viral infections, making early diagnosis challenging without knowledge of potential exposure. Patients typically experience a sudden onset of high fever, usually above 38.6°C (101.5°F), accompanied by profound weakness and fatigue that is often described as more severe than typical flu-like illness.

Severe headache is nearly universal in Ebola patients, often described as the worst headache of the patient's life. Muscle pain (myalgia) and joint pain (arthralgia) are common, affecting the back, legs, and major joints. These early symptoms typically appear 8-10 days after exposure, though the incubation period can range from 2 to 21 days.

• High fever: Temperature typically above 38.6°C (101.5°F), often with chills
• Severe headache: Intense, persistent headache often described as debilitating
• Muscle pain: Generalized myalgia affecting back, limbs, and major muscle groups
• Extreme fatigue: Profound weakness making normal activities impossible
• Sore throat: Pharyngitis and throat discomfort are common early symptoms

Intermediate Symptoms (Days 3-7)

As the disease progresses, gastrointestinal symptoms become prominent and often severe. Patients develop profuse watery diarrhea, which can lead to significant fluid loss and electrolyte imbalances. Vomiting is also common and contributes to dehydration. The combination of diarrhea and vomiting creates a dangerous cycle of fluid loss that, if not properly managed, can lead to hypovolemic shock.

Abdominal pain is frequently reported, often severe and diffuse. Some patients develop a characteristic maculopapular rash, particularly on the trunk, which can help distinguish Ebola from other febrile illnesses. The rash typically appears around day 5-7 of illness and may be more visible on lighter skin.

During this phase, patients may also experience chest pain, hiccups (which can be severe and persistent), and difficulty swallowing. The loss of appetite becomes pronounced, further complicating nutritional and fluid status. Red eyes (conjunctival injection) is common and may be the first sign of bleeding tendency.

Late and Severe Symptoms (After Day 7)

In severe cases, the disease can progress to involve multiple organ systems and cause life-threatening complications. Hemorrhagic manifestations, while not present in all cases, can include bleeding from injection sites, bloody diarrhea, vomiting blood, and bleeding gums. Internal bleeding into the gastrointestinal tract and other organs may occur.

Neurological symptoms may develop, including confusion, agitation, and in severe cases, seizures or coma. Respiratory distress can occur due to fluid accumulation or secondary infections. Multi-organ failure, including kidney and liver dysfunction, often precedes death in fatal cases.

How Is Ebola Transmitted?

Ebola is transmitted through direct contact with the blood, body fluids (including saliva, sweat, urine, vomit, feces, breast milk, and semen), organs, or other bodily secretions of infected people or animals. The virus can also spread through contaminated surfaces and medical equipment. Importantly, Ebola is NOT airborne and cannot spread through casual contact.

Understanding how Ebola spreads is crucial for prevention and control efforts. Unlike airborne diseases such as measles or influenza, Ebola requires direct contact with infectious materials for transmission. This characteristic makes containment possible through proper infection control measures, though challenges remain in resource-limited settings.

The Ebola virus enters the body through broken skin, mucous membranes (eyes, nose, mouth), or sexual contact. Once inside the body, the virus rapidly replicates and spreads through the bloodstream to affect multiple organs. Patients become infectious when they develop symptoms; people who are not showing symptoms cannot spread the disease.

Human-to-Human Transmission

The most common route of Ebola transmission during outbreaks is person-to-person spread within families and healthcare settings. Healthcare workers are at particularly high risk if they care for Ebola patients without adequate personal protective equipment. Family members often become infected while caring for sick relatives or during traditional burial practices that involve washing and preparing the body.

Body fluids that can transmit Ebola include blood, vomit, diarrhea, urine, saliva, breast milk, sweat, tears, and semen. The virus can survive on surfaces and in body fluids for extended periods, particularly in cool, humid environments. Contaminated needles and syringes pose an extremely high risk of transmission and have been responsible for amplifying outbreaks in healthcare settings with inadequate infection control.

Sexual transmission from male survivors has been documented up to 18 months after recovery, as the virus can persist in semen long after it is cleared from the blood. This has important implications for post-recovery counseling and safe sex practices for survivors.

Animal-to-Human Transmission

Ebola outbreaks typically begin when a person comes into contact with an infected animal. Fruit bats of the Pteropodidae family are believed to be the natural reservoir for the Ebola virus, carrying it without becoming ill. Transmission to humans can occur when people handle or consume infected bats or other animals that have been infected by bats.

Primates, including chimpanzees, gorillas, and monkeys, can become infected with Ebola and are often a source of human outbreaks. Forest antelopes and porcupines have also been implicated in transmission. Hunting, butchering, or consuming "bushmeat" (wild animal meat) from infected animals poses significant risk, particularly in regions where these practices are common.

How Is Ebola Diagnosed?

Ebola is diagnosed using laboratory tests including RT-PCR (reverse transcription polymerase chain reaction), which detects viral RNA in blood samples. ELISA tests can detect Ebola antibodies or antigens. Because early symptoms resemble other diseases, diagnosis requires both laboratory confirmation and assessment of potential exposure to the virus.

Diagnosing Ebola presents significant challenges, particularly in the early stages of illness when symptoms are nonspecific and resemble many other common diseases. A thorough patient history, including recent travel to affected areas and potential exposure to infected individuals or animals, is essential for guiding the diagnostic process and determining the need for testing.

Laboratory diagnosis typically requires specialized testing that may not be available in all healthcare facilities. Samples must be handled with extreme care due to the high risk of transmission, and testing is often performed in specialized biosafety level 4 (BSL-4) laboratories. Rapid diagnostic tests are being developed to enable faster diagnosis in field settings during outbreaks.

Laboratory Tests for Ebola

Several laboratory methods are used to confirm Ebola infection, with different tests appropriate at different stages of illness:

• RT-PCR (Reverse Transcription PCR): The gold standard for Ebola diagnosis, RT-PCR detects viral genetic material in blood and can provide results within hours. This test is most reliable when performed 3-10 days after symptom onset.
• Antigen-detection tests: These rapid tests can detect Ebola viral proteins and are useful for field diagnosis during outbreaks, providing results in approximately 30 minutes.
• ELISA (Enzyme-Linked Immunosorbent Assay): Used to detect both viral antigens and antibodies. IgM antibodies appear early in infection, while IgG antibodies develop later and indicate recent or past infection.
• Virus isolation: Growing the virus in cell culture provides definitive diagnosis but requires BSL-4 facilities and takes several days. This method is primarily used for research and strain characterization.

Differential Diagnosis

Because early Ebola symptoms overlap with many other diseases, healthcare providers must consider alternative diagnoses while awaiting test results. Conditions that may present similarly include malaria, typhoid fever, cholera, bacterial meningitis, hepatitis, and other viral hemorrhagic fevers. Patients should be isolated and treated with appropriate precautions until Ebola is ruled out.

How Is Ebola Treated?

Treatment for Ebola includes aggressive supportive care (IV fluids, electrolyte replacement, oxygen therapy) and two FDA-approved treatments: Inmazeb (REGN-EB3) and Ebanga (mAb114). These monoclonal antibody treatments have dramatically improved survival rates when administered early. There is no cure for Ebola, but early, intensive supportive care significantly improves outcomes.

The treatment landscape for Ebola has transformed dramatically since the 2014-2016 West Africa epidemic. While no specific antiviral cure exists, the combination of advanced supportive care and newly approved therapeutic agents has substantially improved survival rates. During the 2018-2020 DRC outbreak, mortality among treated patients dropped significantly compared to historical rates.

The foundation of Ebola treatment remains intensive supportive care, addressing the life-threatening dehydration, electrolyte imbalances, and organ dysfunction that characterize severe disease. Early intervention is critical – patients who receive care within the first few days of symptom onset have significantly better outcomes than those who present later in the illness.

Supportive Care

Supportive care for Ebola patients focuses on replacing lost fluids and electrolytes, maintaining blood pressure, treating secondary infections, and supporting organ function. The massive fluid losses from diarrhea and vomiting require aggressive rehydration, often with several liters of intravenous fluids daily.

Key components of supportive care include:

• Fluid replacement: Intravenous and oral rehydration to combat severe dehydration from diarrhea and vomiting
• Electrolyte management: Monitoring and correcting sodium, potassium, and other electrolyte imbalances
• Oxygen therapy: Supplemental oxygen for patients with respiratory distress
• Blood products: Transfusions for patients with significant bleeding or anemia
• Treatment of secondary infections: Antibiotics for bacterial complications
• Nutritional support: Maintaining adequate nutrition despite severe gastrointestinal symptoms
• Pain management: Appropriate analgesia for comfort

FDA-Approved Treatments

In 2020, the FDA approved two treatments for Ebola Zaire virus infection based on data from the PALM clinical trial conducted during the DRC outbreak. These monoclonal antibody treatments represent a major breakthrough in Ebola therapeutics.

Inmazeb (REGN-EB3) is a combination of three monoclonal antibodies that target the Ebola virus glycoprotein, preventing viral entry into cells. In clinical trials, Inmazeb reduced mortality to 33.5% compared to 51.3% in patients receiving supportive care alone. The treatment is given as a single intravenous infusion.

Ebanga (mAb114) is a single monoclonal antibody also targeting the Ebola glycoprotein. It showed 35.1% mortality compared to 49.7% in the control group. Like Inmazeb, Ebanga is administered as a single IV infusion and can be given alongside supportive care.

How Can Ebola Be Prevented?

Ebola prevention involves vaccination (the Ervebo vaccine is 97.5% effective), avoiding contact with infected body fluids, practicing proper hand hygiene, using personal protective equipment in healthcare settings, and following safe burial practices. In outbreak areas, avoiding bushmeat and contact with wild animals is essential.

Preventing Ebola transmission requires a multi-faceted approach combining vaccination, infection control measures, community education, and public health surveillance. The development of effective vaccines and treatments has transformed the ability to contain outbreaks, but fundamental prevention practices remain essential, particularly in regions with limited healthcare infrastructure.

During outbreaks, prevention efforts focus on identifying and isolating cases, tracing and monitoring contacts, ensuring safe burial practices, and vaccinating high-risk individuals. Community engagement is crucial, as cultural practices and mistrust of healthcare systems have historically contributed to outbreak spread.

Vaccination

The rVSV-ZEBOV vaccine (Ervebo), approved by the FDA in 2019, represents a major breakthrough in Ebola prevention. This live, attenuated vaccine uses a vesicular stomatitis virus engineered to express the Ebola Zaire glycoprotein. Clinical trials during the Guinea outbreak demonstrated approximately 97.5% effectiveness in preventing Ebola infection.

A second vaccine regimen, Zabdeno/Mvabea, provides protection through a two-dose schedule given 8 weeks apart. This vaccine may offer longer-lasting immunity and is approved for use in the European Union. Both vaccines are primarily deployed during outbreaks using a "ring vaccination" strategy, targeting contacts of confirmed cases and healthcare workers.

Infection Control Measures

For healthcare workers and those caring for Ebola patients, strict infection control is essential:

• Personal protective equipment (PPE): Full PPE including gowns, gloves (double-gloving recommended), masks or respirators, face shields, and waterproof aprons
• Hand hygiene: Frequent handwashing with soap and water or alcohol-based hand sanitizer
• Safe injection practices: Using only sterile, single-use needles and syringes
• Environmental cleaning: Proper disinfection of surfaces, equipment, and patient areas with appropriate solutions (0.5% chlorine solution)
• Safe handling of contaminated materials: Careful disposal of all potentially infectious waste

Community Prevention

General population prevention measures include:

• Avoiding contact with blood and body fluids of anyone who may be infected
• Not handling items that may have come in contact with an infected person's body fluids
• Avoiding traditional burial practices that involve direct contact with the deceased
• Avoiding contact with fruit bats, primates, and other wild animals in affected regions
• Not consuming bushmeat or products derived from wild animals
• Seeking medical care promptly if symptoms develop after potential exposure

What Happens After Recovery from Ebola?

Ebola survivors may experience long-term health effects known as "post-Ebola syndrome," including joint pain, fatigue, vision problems, and headaches. The virus can persist in certain body fluids, particularly semen, for months after recovery, requiring survivors to practice safe sex. Many survivors also face social stigma and psychological challenges.

Recovery from Ebola is not the end of the medical journey for many survivors. Research following the West Africa epidemic revealed that a significant proportion of survivors experience persistent health problems, collectively known as post-Ebola syndrome or post-Ebola sequelae. Understanding these long-term effects is essential for providing comprehensive care to survivors.

The development of immunity in survivors is an area of active research. Studies suggest that survivors develop antibodies that provide protection against reinfection with the same strain of Ebola, though the duration of this protection is not fully established. Some survivors have participated in convalescent plasma donation programs, providing antibodies to treat other patients.

Long-Term Health Effects

Common post-Ebola symptoms include:

• Musculoskeletal pain: Joint and muscle pain affecting mobility and quality of life
• Chronic fatigue: Persistent, debilitating fatigue lasting months or years
• Ocular problems: Eye inflammation (uveitis), vision changes, and in some cases, blindness
• Headaches: Frequent or chronic headaches not present before infection
• Neurological symptoms: Memory problems, concentration difficulties, and mood changes
• Hearing loss: Partial or complete hearing impairment

Viral Persistence

One of the most significant findings from survivor studies is that Ebola virus can persist in certain "immune-privileged" sites in the body long after it is cleared from the blood. The most important of these is semen, where the virus has been detected up to 18 months after recovery. This has implications for sexual transmission and requires survivors to undergo testing and practice safe sex.

The virus has also been found in breast milk, ocular fluid, and the central nervous system. In rare cases, viral persistence has led to disease recurrence or transmission to partners. WHO recommends that male survivors abstain from sexual activity or use condoms until their semen has tested negative for the virus twice.

Major Ebola Outbreaks in History

The largest Ebola outbreak occurred in West Africa (2014-2016), causing over 28,000 cases and 11,000 deaths. Other significant outbreaks include the 2018-2020 DRC outbreak (3,481 cases) and the 1976 outbreaks that first identified the disease. Each outbreak has contributed to improved understanding and response capabilities.

Since its discovery in 1976, Ebola has caused numerous outbreaks, primarily in Central and West Africa. Each outbreak has presented unique challenges and contributed to our understanding of the disease and how to combat it. The response to major outbreaks has driven advances in diagnostics, treatments, and vaccines that are now deployed globally.

The 2014-2016 West Africa Epidemic

The West Africa Ebola epidemic remains the largest and most complex outbreak in history. Beginning in Guinea in December 2013 and spreading to Liberia and Sierra Leone, the epidemic ultimately caused 28,616 confirmed, probable, and suspected cases and 11,310 deaths. The outbreak overwhelmed healthcare systems, disrupted economies, and revealed critical gaps in global health security preparedness.

The epidemic led to unprecedented international response, including deployment of military and humanitarian resources, construction of Ebola treatment units, and massive community engagement campaigns. The lessons learned directly informed the development of vaccines and treatments now available, as well as improvements in global outbreak response mechanisms.

Recent Outbreaks in the Democratic Republic of Congo

The DRC has experienced more Ebola outbreaks than any other country, owing to the presence of the virus in local fruit bat populations. The 2018-2020 outbreak in North Kivu and Ituri provinces was particularly challenging, occurring in an active conflict zone. Despite these challenges, it provided the opportunity to test the Ervebo vaccine and new treatments in real-world conditions.