Ebola disease is a rare but severe illness caused by infection with viruses that primarily affect people in parts of Africa. The disease can progress from flu-like symptoms to serious complications, including bleeding and organ failure. While outbreaks have occurred regularly since the 1970s, modern medical advances have improved survival rates, and vaccines are now available to help protect against certain types of the virus.
Understanding Ebola Disease in Today’s World
Ebola disease is caused by a group of viruses known as orthoebolaviruses, which are microscopic infectious agents that can cause severe illness in humans and some animals. These viruses were first discovered in 1976 in the Democratic Republic of the Congo, near the Ebola River, which gave the disease its name. At that time, the world witnessed two simultaneous outbreaks in different parts of Central Africa, marking the beginning of a new health challenge that would resurface repeatedly over the decades.[1]
The disease belongs to a category of illnesses called viral hemorrhagic fevers, which are infections that damage blood vessels and can lead to bleeding problems. When someone develops Ebola disease, their immune system goes into overdrive, triggering a cascade of reactions throughout the body that can affect multiple organs at once. This aggressive response explains why the disease can be so dangerous and why quick medical attention is crucial.[3]
There are four different types of orthoebolaviruses that cause illness in people. The Ebola virus, also called Zaire ebolavirus, is the most common cause of outbreaks and has historically been the most deadly. Sudan virus causes a similar disease and is also quite dangerous. Bundibugyo virus is less likely to cause death compared to the other types. Finally, Taï Forest virus is the rarest of all and has caused very few documented cases in humans.[1]
Where Ebola Disease Occurs and Who It Affects
Ebola disease occurs primarily in countries located in sub-Saharan Africa, particularly in West, Central, and East Africa. The virus exists naturally in certain animals in these regions, and outbreaks typically begin when humans come into close contact with infected wildlife. For many years after the initial discovery in 1976, the disease appeared sporadically in remote villages close to tropical rainforests.[5]
Between 1979 and 1994, no human cases were detected anywhere in the world. However, since 1994, outbreaks have been recognized with increasing frequency. Most confirmed cases have been reported from countries including the Democratic Republic of the Congo, Gabon, the Republic of the Congo, Sudan, and Uganda. Until 2014, these outbreaks remained largely confined to rural areas far from major population centers.[5]
The largest Ebola outbreak in history occurred between 2014 and 2016 in West Africa. This outbreak was unprecedented because it affected urban areas for the first time, leading to intense transmission in cities with large populations. The outbreak involved Guinea, Liberia, and Sierra Leone primarily, and resulted in more than 28,000 reported cases and over 11,000 deaths across ten countries. This event demonstrated how quickly the disease could spread when it reached densely populated areas, and it also led to imported cases in countries including Italy, Mali, Nigeria, Senegal, Spain, the United Kingdom, and the United States.[5][4]
The average case fatality rate for Ebola disease is around 50 percent, meaning that about half of infected people may die from the illness. However, this rate has varied considerably across different outbreaks, ranging from as low as 25 percent to as high as 90 percent. The variation depends on many factors, including the specific virus type involved, how quickly patients receive medical care, the quality of healthcare available, and whether the outbreak occurs in a remote area or near medical facilities. Without treatment, the mortality rate can be as high as 80 to 90 percent.[2][1]
What Causes Ebola Disease
The natural home of orthoebolaviruses is believed to be in certain animals, particularly fruit bats of the Pteropodidae family. Scientists think these bats can carry the virus without becoming sick themselves, making them what researchers call a natural reservoir for the disease. Other animals can also become infected, including chimpanzees, gorillas, monkeys, forest antelopes, and porcupines. When these animals contract the virus, they often become seriously ill or die.[2]
Humans typically get infected with the virus when they have close contact with the blood, secretions, organs, or other bodily fluids of infected animals. This often happens when people hunt wild animals for food, a practice sometimes called bushmeat hunting, or when they come across sick or dead animals in the forest. In some communities, traditional practices involving handling of wild animals for food or other purposes can create opportunities for the virus to jump from animals to humans.[2]
Once the first person in a community becomes infected through contact with an animal, the virus can then spread from person to person. This human-to-human transmission is how outbreaks develop and expand. The virus enters the body through broken skin or through mucous membranes, which are the moist tissues that line the eyes, nose, and mouth. Once inside the body, the virus infects many different types of cells, multiplying rapidly and overwhelming the body’s defenses.[13]
Groups at Higher Risk of Infection
Healthcare workers and family members who care for someone with Ebola disease face the highest risk of becoming infected themselves. This elevated risk exists because these individuals have the most frequent and direct contact with sick patients and their bodily fluids. When proper infection control measures are not followed consistently, caregivers can easily become exposed to the virus through contaminated surfaces, medical equipment, or direct contact with patients.[1]
During the West African outbreak from 2014 to 2016, many healthcare workers became infected, especially in the early stages before the full extent of the crisis was understood. In some cases, critically ill patients with severe symptoms were brought to hospitals where staff were unaware of the risks of being exposed to patient blood and body fluids without proper protection. This lack of awareness and inadequate protective equipment led to numerous infections among medical personnel.[4]
People who participate in traditional burial practices are also at increased risk. In some African cultures, it is customary for family members and community members to wash and prepare the body of a deceased loved one before burial. However, the bodies of people who have died from Ebola disease remain highly infectious, and direct contact with these bodies can transmit the virus to those performing the burial rituals. Safe burial practices that minimize direct contact are essential during outbreaks.[2]
Individuals who handle or consume wild animals in regions where the virus exists also face increased risk. Hunters, butchers, and people who prepare bushmeat can be exposed to the virus if the animals they handle are infected. Even touching or eating undercooked meat from infected animals can lead to transmission of the disease.[3]
How Ebola Disease Spreads Between People
Ebola disease spreads through direct contact with the body fluids of a person who is sick with the disease or has died from it. Body fluids include blood, urine, feces, saliva, sweat, vomit, breast milk, amniotic fluid, semen, and vaginal fluid. The virus can enter a healthy person’s body through broken skin or through the mucous membranes of the eyes, nose, or mouth. This means that touching an infected person’s fluids with your hands and then touching your face could lead to infection.[1]
An important aspect of Ebola transmission is that people with the disease do not spread the virus until they begin showing symptoms. During the incubation period, which is the time between exposure to the virus and the appearance of symptoms, infected individuals are not contagious and pose no risk to others around them. Once symptoms begin, however, the person becomes capable of transmitting the virus to others through their bodily fluids.[6]
As the disease progresses and symptoms become more severe, the amount of virus in the body increases, making the infected person more contagious. In the early days of symptoms when the illness is mild, transmission is less likely compared to later stages when symptoms are severe. This is why many family members living in the same home with an Ebola patient do not necessarily become infected, especially if they take precautions to avoid contact with body fluids.[21]
The virus can also spread through contact with objects or surfaces that have been contaminated with infected body fluids. This includes items such as clothing, bedding, needles, medical equipment, and even toilets used by someone with the disease. If these contaminated objects are touched and then a person touches their face or has an open wound, transmission can occur. This is why thorough cleaning and disinfection of surfaces in healthcare settings and homes where Ebola patients are cared for is crucial.[1]
Sexual transmission is another important route of spread. The virus can be transmitted through vaginal, oral, or anal sexual intercourse with an infected person. Even after someone has recovered from Ebola disease, the virus can persist in certain body fluids, particularly semen. Men who have recovered from the disease can carry the virus in their semen for at least 12 months after recovery. This means they can potentially transmit the virus to sexual partners long after they have gotten better from the illness.[3][18]
Pregnant women with Ebola disease can transmit the virus to their unborn babies during pregnancy, during delivery, or through breastfeeding. Similarly, babies born to mothers who are infected can become ill themselves. The virus can also be present in breast milk, meaning that mothers who have or have had Ebola should not breastfeed their infants until testing confirms the virus is no longer present.[18]
Recognizing the Symptoms of Ebola Disease
The time between exposure to the virus and the appearance of symptoms ranges from 2 to 21 days, though most commonly symptoms begin 8 to 10 days after contact with the virus. This period is called the incubation period. Understanding this timeframe is important because it helps healthcare workers identify people who may have been exposed and monitor them for signs of illness.[1]
Early symptoms of Ebola disease often resemble those of influenza or other common illnesses, which can make diagnosis challenging in the beginning. These initial symptoms are sometimes called “dry” symptoms and include sudden fever, severe headache, muscle pain, joint pain, weakness, fatigue, chills, sore throat, and loss of appetite. At this stage, many people might think they have malaria or another common infection rather than Ebola.[1][3]
As the disease progresses over the following days, symptoms typically become more severe and distinctive. The illness advances to what are called “wet” symptoms, which include severe diarrhea, vomiting, and stomach pain. These symptoms can lead to severe dehydration, which makes the person feel extremely weak and confused. The diarrhea and vomiting can be so severe that patients lose large amounts of fluids very quickly, making rehydration a critical part of treatment.[1]
In later stages of the disease, some patients develop bleeding and bruising. This can manifest as red or bloodshot eyes, bleeding from the gums, blood in the urine or stool, or vomiting that contains blood or looks like coffee grounds. Some people develop a rash or small spots of blood under the skin. Not all Ebola patients experience bleeding symptoms, but when they occur, they indicate that the disease has reached an advanced and dangerous stage.[3]
The most severe complications of Ebola disease can include brain inflammation, which may cause confusion and seizures; organ failure, particularly affecting the kidneys and liver; and shock, which occurs when the body doesn’t receive enough blood flow to vital organs. These late-stage complications are life-threatening and require intensive medical support.[3]
Preventing Ebola Disease
When living in or traveling to regions where Ebola viruses may be present, there are several important steps people can take to protect themselves from infection. The most fundamental principle is to avoid contact with body fluids from people and animals. This means avoiding blood and all body fluids such as urine, feces, saliva, sweat, vomit, breast milk, semen, and vaginal fluids from people who are sick or who have died from any unknown illness.[1]
Good hand hygiene is one of the most effective preventive measures. Washing hands frequently with soap and water helps remove the virus if it has been picked up from contaminated surfaces or objects. When soap and water are not available, using an alcohol-based hand sanitizer is the next best option. It’s particularly important to wash hands before eating, after using the toilet, and after any potential contact with sick individuals or contaminated surfaces.[18]
In areas where Ebola outbreaks are occurring, people should avoid all high-risk places and activities. This includes staying away from healthcare facilities where Ebola patients are being treated unless absolutely necessary for medical care. If visiting such facilities is unavoidable, proper protective equipment including masks, gloves, gowns, and goggles should be worn. Similarly, participation in funeral or burial practices that involve direct contact with bodies should be avoided, or if participation is necessary, appropriate protective measures must be used.[1][18]
Avoiding contact with wild animals is another important preventive measure. In regions where Ebola occurs, people should not handle bats, monkeys, gorillas, chimpanzees, forest antelopes, or porcupines, whether these animals are alive, sick, or dead. Consumption of bushmeat should be avoided entirely, as handling or eating meat from infected animals can transmit the virus. No animals in countries outside of Africa have been found to naturally carry Ebola viruses.[1][18]
Sexual practices also require attention for prevention. People should avoid sexual contact with anyone who is currently sick with Ebola disease. For men who have recovered from Ebola, it’s important to avoid sexual activity for at least 12 months after recovery, or to use condoms consistently and correctly during this period. This precaution is necessary because the virus can remain in semen for many months after the acute illness has resolved.[18]
An FDA-approved vaccine is now available for the prevention of Ebola virus disease caused by Zaire ebolavirus. This vaccine has shown high effectiveness in protecting people from infection. During the 2014 outbreak, a study found that among people who received the vaccine, no Ebola cases were recorded 10 days or more after vaccination, while there were 23 cases among those who did not receive the vaccine. The vaccine is particularly important for healthcare workers, laboratory personnel, and others who may be at increased risk of exposure.[1][12]
How Ebola Disease Affects the Body
When orthoebolaviruses enter the body, they do so through mucous membranes, breaks in the skin, or directly into the bloodstream through contaminated needles or other sharp objects. Once inside, these viruses are remarkably effective at infecting many different types of cells throughout the body. Unlike some viruses that target only specific organs or tissues, Ebola viruses can infect cells in the liver, spleen, lymph nodes, blood vessels, and other organs.[13]
One of the key features of Ebola disease is how it affects the immune system. When the virus infects immune cells, it triggers an overwhelming immune response where the body releases large amounts of signaling molecules called cytokines. This flood of cytokines, sometimes called a “cytokine storm,” causes inflammation throughout the body and can damage blood vessels. The damaged blood vessels become leaky, allowing fluid to escape from the bloodstream into surrounding tissues. This leads to low blood pressure and reduces blood flow to vital organs.[3]
The virus also interferes with blood clotting mechanisms. It affects cells called platelets that normally help blood clot when we get injured. At the same time, it can trigger inappropriate clotting inside blood vessels throughout the body, a condition called disseminated intravascular coagulation. This uses up the body’s clotting factors, which paradoxically leads to bleeding because there are not enough clotting factors left when they are needed. This explains why some patients experience bleeding from various sites, including the gums, nose, or internally in the stomach or intestines.[12]
The liver is often severely affected by Ebola infection. The virus infects liver cells and causes them to die, leading to liver dysfunction. When the liver doesn’t work properly, it cannot perform its normal functions such as producing clotting factors, processing toxins, or producing important proteins. This liver damage contributes to the bleeding problems and can also cause jaundice, where the skin and eyes turn yellowish.[13]
The kidneys can also be damaged both directly by the virus and indirectly by reduced blood flow and dehydration. Kidney failure means the body cannot properly filter waste products from the blood or maintain the right balance of fluids and electrolytes. Similarly, the heart, lungs, and brain can be affected, leading to breathing difficulties, confusion, seizures, or even coma in severe cases.[3]
An interesting aspect of Ebola disease is that the virus can persist in certain parts of the body even after a person has recovered from the acute illness. These areas, called immunologically privileged sites, include the testes, the interior of the eyes, the placenta in pregnant women, and the central nervous system. In these locations, the virus is somewhat protected from the immune system and can remain for several months. This explains why recovered men can still have the virus in their semen long after they feel better, and why some survivors experience complications such as vision problems or joint pain months after recovery.[14]
