Ebola

• 1. Introduction

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  Ebola kills, on average, half of everyone it infects. That single statistic sits at the heart of why this disease has shaped public health responses, international emergency declarations, and the daily decisions of medical workers across sub-Saharan Africa for nearly five decades. In the worst recorded outbreak, the death rate reached 90 percent. In the mildest, it still took one in four lives. Ebola virus disease, known also as EVD and Ebola hemorrhagic fever, is caused by four of six known ebolaviruses and can move from animals to humans before spreading between people through direct contact with blood and body fluids. Since it was first identified in 1976, it has returned again and again, in intermittent waves, mostly across tropical regions of sub-Saharan Africa. What follows is the story of how scientists came to understand the virus, how communities and governments have tried to stop it, and how a disease that once had no approved treatment or vaccine has slowly, imperfectly, begun to meet its match.

• 2. Discovery and Naming

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  On the 27th of June 1976, a storekeeper at a cotton factory in Nzara, in what was then Sudan, was hospitalized with symptoms no one could immediately explain. He died on the 6th of July. That event, the very first identifiable case of what would come to be called Ebola, was not fully understood as a new disease until months later, after a second outbreak had already begun in a different country.

  On the 26th of August 1976, a village school headmaster named Mabalo Lokela began showing symptoms in Yambuku, a small rural community in the Mongala District of northern Zaire. Lokela had recently returned from a trip near the Ebola River, along the border with the Central African Republic, which he had visited between the 12th and the 22nd of August. Doctors initially believed he had malaria and gave him quinine. His condition kept worsening, and he was admitted to Yambuku Mission Hospital on the 5th of September. He died on the 8th of September, fourteen days after his symptoms began.

  As others in Yambuku who had contact with Lokela began to die, the country's Minister of Health and President Mobutu Sese Seko declared the entire region a quarantine zone, closing roads, waterways, and airfields under martial law and shutting down schools and businesses. The initial response was led by Congolese doctors, including Jean-Jacques Muyembe-Tamfum, one of the discoverers of Ebola. Muyembe was also the first scientist to have direct contact with the disease and survive. He took a blood sample from a Belgian nun; that sample was later used by researcher Peter Piot to identify the previously unknown virus.

  Piot, who co-discovered Ebola, arrived with a CDC team to assess the outbreak and observed that the whole region was in panic. He concluded that Belgian nuns had inadvertently started the epidemic by giving unnecessary vitamin injections to pregnant women without sterilizing the needles and syringes. The outbreak in Zaire lasted 26 days; researchers believed it subsided because of local precautions, the quarantine, and the cessation of those injections. In Zaire alone, 318 people were infected and 280 died, an 88% fatality rate.

  The virus strain was named after the Ebola River, near where the first-identified outbreak site in Zaire was located. The two 1976 outbreaks were initially thought to be connected, but scientists later determined they were caused by two distinct viruses: the Sudan ebolavirus and the Zaire ebolavirus.

• 3. How the Virus Works

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  Ebola virions are filamentous particles, sometimes shaped like a shepherd's crook, a U, or a 6. They are 80 nanometers wide and can be as long as 14,000 nanometers. That distinctive shape, visible under electron microscopy, was one of the first clues that Ebola belonged to a new category of virus.

  Once inside the body, the virus attaches to specific receptors on cell surfaces and fuses with cellular membranes. Its structural glycoprotein, known as GP1,2, is responsible for binding to and infecting target cells. Among the first cells infected are macrophages, which are a type of immune cell. Their infection triggers programmed cell death and sets off a cascade that weakens the body's defenses across the board.

  Endothelial cells, which line the inside of blood vessels, may be infected within three days of exposure. As the glycoprotein damages these cells, it reduces the availability of the proteins responsible for cell adhesion and causes liver damage, which in turn impairs the body's ability to clot blood properly. The widespread bleeding that can follow leads to swelling and shock from blood loss.

  EBOV also actively disables the immune system's early warning mechanisms. The virus's VP35 protein directly blocks the production of interferon-beta, while the VP24 protein prevents a key signaling protein called STAT1 from entering the nucleus of neighboring cells. This stops those cells from producing the antiviral proteins that would normally slow the virus's spread. By disabling these defenses, the virus can replicate rapidly in macrophages, liver cells, dendritic cells, and adrenal gland cells before the body has a chance to mount a coordinated response.

• 4. Symptoms and Survival

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  Between two and twenty-one days after exposure, a person infected with Ebola typically begins to feel what resembles a sudden and severe flu: fatigue, fever above 38.3 degrees Celsius, muscle and joint pain, headache, and sore throat. The incubation period is usually between four and ten days, though mathematical models suggest around five percent of cases may take longer than twenty-one days to develop.

  Vomiting, diarrhea, and abdominal pain follow, often leading to severe dehydration. In about half of cases, a maculopapular rash, described as a flat red area covered with small bumps, appears five to seven days after symptoms begin. Bleeding, when it occurs, typically starts five to seven days in as well. Bleeding from mucous membranes or needle puncture sites has been reported in 40-50% of cases. Heavy gastrointestinal bleeding is less common: it was reported in roughly 58% of cases during the 2001 outbreak in Gabon, but only around 18% in the 2014-15 outbreak in the United States, a difference attributed partly to better prevention of a clotting disorder known as disseminated intravascular coagulation.

  Death, when it comes, follows typically six to sixteen days after the first symptoms and is usually caused by shock from fluid loss. Those who survive may begin recovering between seven and fourteen days after onset. But recovery is not always complete. A large portion of survivors develop what is called post-Ebola virus syndrome: long-term problems including joint and muscle pain, liver inflammation, hearing loss, vision problems, fatigue, and sleep disturbances. Survivors are advised to wear condoms for at least twelve months after initial infection, or until semen tests negative for the virus on two separate occasions. Antibodies developed after infection last at least ten years, though whether they prevent re-infection remains unclear.

• 5. How Ebola Spreads

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  Fruit bats are considered the most likely natural reservoir of ebolaviruses. Three species, Hypsignathus monstrosus, Epomops franqueti, and Myonycteris torquata, have been found to potentially carry the virus without becoming sick. In a 2002-2003 survey of 1,030 animals from Gabon and the Republic of the Congo, between 2.2 and 22.6% of bats sampled at various periods showed evidence of Ebola infection. Bats were also known to roost in the cotton factory where the first cases of both the 1976 and 1979 outbreaks were observed.

  Animals such as chimpanzees, gorillas, and duikers can become infected when they eat fruit partially consumed by infected bats. The carcasses of gorillas and chimpanzees have served as sources of human infection during outbreaks in 2001 and 2003. Areas undergoing deforestation carry a heightened risk, as changes to the landscape bring wildlife into closer contact with human communities.

  Between people, Ebola spreads only through direct contact with the blood or body fluids of someone who is showing symptoms. Body fluids that may carry the virus include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine, and semen. The virus can survive on objects for a few hours in a dried state and for a few days within body fluids outside the body. Dead bodies remain infectious, and in Guinea during the 2014 outbreak, 69% of Ebola infections were believed to have been contracted through contact with infected corpses during burial rituals.

  Airborne transmission between humans has not been documented during any outbreak. Pigs with EVD develop very high concentrations of the virus in their lungs rather than their blood, allowing them to potentially spread the virus through coughing or sneezing without direct contact. Humans and other primates accumulate the virus in the blood rather than the lungs, which researchers believe is why airborne transmission has not been observed between people even in experimental conditions.

• 6. The West Africa Epidemic

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  Researchers traced the 2013-16 West African Ebola epidemic to a one-year-old child who died in December 2013 in Guinea. By March 2014, the WHO had reported the outbreak publicly. It spread rapidly to Liberia and Sierra Leone, becoming the largest Ebola outbreak ever documented and the first in the region.

  On the 8th of August 2014, the WHO declared the epidemic an international public health emergency. The WHO Director-General urged the international community to act, stating that the affected countries simply did not have the capacity to manage an outbreak of that size and complexity on their own. By mid-August 2014, Doctors Without Borders described the situation in Monrovia, Liberia's capital, as catastrophic and deteriorating daily. Fears of Ebola had shut down much of the city's health system, leaving patients without care for unrelated conditions. In a statement issued on the 26th of September 2014, the WHO described the epidemic as the most severe acute public health emergency seen in modern times.

  By August 2014, the WHO reported that 10% of the dead were healthcare workers. In September 2014, the capacity gap for treating Ebola patients was estimated at 2,122 beds. By December of that year, enough beds existed to treat all reported cases, though the uneven geographic distribution of patients caused serious shortfalls in some areas.

  The epidemic also spread beyond Africa. Eric Duncan flew from Liberia to Texas on the 19th of September 2014 and began showing symptoms five days later. He died on the 8th of October and was the first case diagnosed in the United States. In early October 2014, a 44-year-old Spanish nurse named Teresa Romero contracted Ebola after caring for a repatriated priest, making her the first person known to have acquired the virus outside Africa. On the 29th of December 2015, forty-two days after the last person tested negative a second time, Guinea was declared free of Ebola transmission. The outbreak was declared no longer an emergency on the 29th of March 2016.

• 7. Vaccines and Treatment

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  An Ebola vaccine called rVSV-ZEBOV was approved by the US FDA in December 2019. It appears to be fully effective ten days after being administered. It was studied in Guinea between 2014 and 2016, and more than 100,000 people had been vaccinated against Ebola as of the time of reporting. During the Kivu Ebola epidemic from 2018 to 2020, the WHO reported that approximately 345,000 people received the vaccine.

  In October 2020, the FDA approved a three-drug combination called atoltivimab/maftivimab/odesivimab, sold under the name Inmazeb, specifically for treating infection caused by the Zaire ebolavirus. A second treatment, ansuvimab, has also been shown to improve outcomes. In trials, these two experimental treatments were found to be 90% effective. Before these approvals, treatment was primarily supportive, focused on rehydration and managing symptoms.

  Early care remains critical regardless of which treatments are available. Oral rehydration therapy, using slightly sweetened and salty water, and intravenous fluids both improve survival rates considerably when started early. The WHO advises against aspirin or ibuprofen because of the bleeding risk they carry in EVD patients. A rapid antigen test approved by the WHO in 2015 can confirm Ebola in 92% of those affected and rule it out in 85% of those not affected, with results available in fifteen minutes. In 2014, mobile testing facilities deployed in Liberia reduced the time from sample submission to result to just 3-5 hours, a meaningful improvement in a disease where early isolation and treatment are decisive.

• 8. Outbreaks and Ongoing Risk

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  Between 1976 and 2013, the WHO recorded 2,387 confirmed cases of Ebola resulting in 1,590 deaths across 24 outbreaks. The disease has returned to the Democratic Republic of the Congo repeatedly: a 2003 outbreak in the DRC killed 128 of 143 infected, a 90% death rate that stands as the highest of any ebolavirus genus outbreak. A 2007 outbreak in a four-village region of the DRC eventually infected 264 people and killed 187, following the death of a local village chief whose funeral brought many people into contact.

  On the 1st of August 2018, the DRC's 10th Ebola outbreak was declared in North Kivu province, the first to occur in an active military conflict zone. By November 2018, nearly 200 Congolese had died of Ebola, roughly half from the city of Beni, where armed groups fighting over mineral wealth impeded medical relief efforts. By July 2019, the outbreak had grown to become the second largest ever recorded, with more than 2,025 confirmed and probable cases and 1,357 deaths. On the 17th of July 2019, the WHO declared it a global health emergency, the fifth such declaration the organisation had ever made.

  In February 2021, Sakoba Keita, head of Guinea's national health agency, confirmed that a new outbreak in the south-eastern region near Nzérékoré may have started from a latent case reactivating in a survivor of an earlier outbreak, a finding with significant implications for long-term surveillance of survivors. On the 15th of May 2026, the DRC Ministry of Health declared the country's 17th Ebola epidemic, in Ituri province. Just two days later, on the 17th of May 2026, the WHO Director-General declared it a Public Health Emergency of International Concern, following reports of 246 suspected cases, 80 deaths, and 8 laboratory-confirmed cases in the DRC, plus 2 additional confirmed cases and one death in Uganda. As of the 24th of May 2026, the number of suspected cases in the DRC had risen above 900.