Ebola kills roughly half the people it infects, with fatality rates ranging from about 33% to 67% depending on the strain. That makes it one of the deadliest infectious diseases known, though modern treatment and vaccination have significantly improved the odds for people who get care quickly.
Fatality Rates by Strain
Not all Ebola viruses are equally lethal. There are four strains known to cause disease in humans, and they differ dramatically in how dangerous they are. The Zaire strain, responsible for the largest outbreaks including the 2014 West African epidemic, has an average fatality rate of about 67%. The Sudan strain kills roughly 49% of those infected. The most recent Sudan virus outbreak, in Uganda in 2022, caused 164 cases and 55 confirmed deaths. The Bundibugyo strain is the least deadly of the three major strains, with a fatality rate around 33%.
These averages mask a wide range. Individual outbreaks have seen fatality rates as low as 25% and as high as 90%, depending on the speed of the response, the quality of available care, and how quickly patients sought treatment.
What Actually Kills You
Ebola doesn’t kill through a single mechanism. It attacks multiple organ systems at once, creating a cascade of failures that overwhelms the body. The virus directly invades cells in the liver, kidneys, and blood vessels, while simultaneously triggering a massive immune overreaction sometimes called a “cytokine storm.” Your immune system floods the body with inflammatory signals so aggressively that it damages your own tissues.
This combination causes blood vessels to leak fluid, blood pressure to drop, and organs to shut down. The kidneys fail from a mix of direct viral damage and tiny blood clots blocking their filtration system. The lungs fill with fluid. Bleeding, when it occurs, typically appears in the final hours before death rather than being a prolonged symptom. Many patients also develop secondary bacterial infections as their immune system is redirected toward fighting the virus, creating something resembling severe sepsis on top of everything else.
Viral load in the blood is one of the strongest predictors of outcome. People who die tend to have higher and faster-rising virus levels than survivors, with the peak occurring about two days later and staying elevated until death.
The Critical Window
The timeline from illness to death is brutally fast. In studied outbreaks, the median time from first symptoms to hospital admission was about 6 days, and the median time from admission to death was just 3.5 days. That leaves a narrow window for treatment to make a difference, which is why early intervention matters so much.
Patients who reached treatment centers sooner in the 2014 West African outbreak had significantly better outcomes than those admitted later. By the time organ failure sets in, reversing the damage becomes exponentially harder.
How Treatment Has Changed the Odds
Before 2014, the average mortality across Ebola outbreaks was around 70%. That number has dropped substantially as care has improved. During the West African epidemic, mortality fell to about 39% in treatment centers. Patients treated in well-resourced hospitals in Europe and the United States had a fatality rate of roughly 18.5%.
The difference comes down to aggressive supportive care: replacing lost fluids, maintaining blood pressure, and managing organ function as the body fights the virus. These interventions don’t target the virus directly, but they keep patients alive long enough for the immune system to clear it.
Two targeted treatments now exist as well. One approved therapy reduced the 28-day fatality rate to 35% compared to 49% in control groups. Even among patients with the highest viral loads, who face the worst prognosis, it brought mortality down from about 85% to 70%. These aren’t cures, but they represent a meaningful improvement layered on top of supportive care.
Vaccines Offer Strong Protection
A vaccine targeting the Zaire strain has been available since 2019 and has proven highly effective. In clinical trials, it showed 100% efficacy at preventing disease among vaccinated individuals. Real-world data from the 2018-2020 outbreak in the Democratic Republic of the Congo put its effectiveness at around 84% when measured 10 or more days after vaccination. The gap between trial and real-world numbers is common with vaccines and reflects the messier conditions of an active outbreak, including cold chain challenges and delayed vaccination.
No equivalent vaccine exists yet for the Sudan strain, which drove the 2022 Uganda outbreak.
How It Spreads
Ebola spreads through direct contact with the body fluids of an infected person. Blood carries the highest viral load, reaching concentrations as high as 10 million RNA copies per milliliter within just two days of symptoms appearing. The virus has also been isolated from saliva, urine, semen, breast milk, and the fluid inside the eye.
Outside the body, the virus is more durable than many people assume. It can survive up to 3 days on protective clothing in tropical conditions, up to 8 days in wastewater, and up to 46 days in blood-based liquid at room temperature. This persistence is part of why burial practices involving contact with deceased patients have been a major transmission route in outbreaks, since viral loads in people who die are especially high.
Ebola is not airborne. You cannot catch it from someone across a room. Transmission requires contact with infected fluids, either directly or through contaminated surfaces. This makes it far less contagious than respiratory viruses, but the high fatality rate means even limited spread can cause devastating outbreaks in communities without rapid containment.
Life After Survival
Surviving Ebola doesn’t mean a clean return to health. In a study of 326 survivors assessed about a year after their acute illness, 76% reported at least one new health problem that developed after their infection. The most common complaints were joint pain, headache, and fatigue. Nearly two-thirds of survivors dealt with two or more of these symptoms simultaneously, and in 86% of those affected, the symptoms significantly interfered with daily life.
Perhaps most concerning, these complications barely improved over time. Follow-up over approximately three years showed little change in the proportion of survivors reporting symptoms. Women were more likely to experience headaches, while older survivors were more prone to musculoskeletal and vision problems. The mechanisms behind these long-term effects aren’t fully understood, but they appear connected to persistent inflammation triggered during the acute infection.