West African Ebola Epidemic (2013-2016): The Largest Outbreak

The West African Ebola epidemic was the largest outbreak of Ebola virus disease ever recorded. Beginning in a Guinean village in December 2013, it spread to Liberia and Sierra Leone and over two and a half years caused about 28,600 recorded cases and more than 11,300 deaths. The crisis exposed weaknesses in national health systems and in the world’s emergency response, and it led to the first proven Ebola vaccine.

What Ebola is

Ebola virus disease is a severe illness caused by viruses of the genus Ebolavirus, first identified in 1976 near the Ebola River in what is now the Democratic Republic of the Congo. The strain in West Africa was Zaire ebolavirus, the most lethal type. It causes fever, weakness, vomiting and diarrhoea and, in some patients, bleeding; many deaths result from fluid loss and organ failure.

The virus spreads through direct contact with the blood or body fluids of a sick person, or with the bodies of people who have died of the disease. It is not airborne in the way flu is. That meant carers, health workers and mourners who washed and touched bodies were at the highest risk. Before 2014 all outbreaks had been in Central and East Africa and had involved, at most, a few hundred cases.

Origins in Guinea

Investigators later traced the first known case to a child of about 18 months in the village of Meliandou, Guéckédou prefecture, in the forested south-east of Guinea, who fell ill in late December 2013 and died within days. The original animal source was never confirmed; fruit bats are the suspected natural reservoir, and one study pointed to insect-eating bats roosting near the village.

Because Ebola had never been seen in West Africa, the early deaths were mistaken for cholera, Lassa fever or malaria. The virus moved along trade routes to nearby towns and across the borders with Liberia and Sierra Leone, which meet close to Guéckédou. Only on 23 March 2014 did Guinea’s health ministry and WHO announce an Ebola outbreak, by which time it had already spread widely.

The epidemic grows

Cases appeared in Liberia in March 2014 and in Sierra Leone in May. After an apparent lull, transmission exploded in mid-2014, when the virus reached the capitals Monrovia, Freetown and Conakry. In June the medical charity Médecins Sans Frontières warned that the outbreak was out of control and that it lacked the staff to cope.

The three countries were among the poorest in the world. Liberia and Sierra Leone were still rebuilding after long civil wars, including the Sierra Leone Civil War, and had very few doctors per head of population. Treatment centres were overwhelmed and turned patients away; sick people died at home and infected relatives. Distrust of governments, fear and rumours led some families to hide patients.

Health workers paid a heavy price. WHO counted about 880 infections and more than 500 deaths among health workers, including the leading Sierra Leonean virologist Sheik Humarr Khan, who died in July 2014. Governments imposed emergency measures: Liberia quarantined the crowded Monrovia district of West Point in August 2014, and Sierra Leone confined its whole population to their homes for three days in September 2014 while teams went door to door.

International response

On 8 August 2014 WHO declared a Public Health Emergency of International Concern. Critics, including MSF, argued that the declaration came months too late and that the world had been slow to send help. On 18 September 2014 the UN Security Council adopted Resolution 2177, calling Ebola a threat to international peace and security, and the UN created its first-ever emergency health mission, UNMEER.

Foreign governments then sent personnel and money on a large scale. The United States deployed military engineers and logistics teams to Liberia under Operation United Assistance, building treatment units; Britain led support for Sierra Leone and France for Guinea. Cuba sent hundreds of doctors and nurses. China, the African Union and many charities also contributed.

Equally important was work by local communities: safe burial teams, contact tracers, survivors who cared for patients because they were immune, and religious leaders who encouraged people to change funeral practices. By early 2015 case numbers were falling in all three countries.

Cases beyond the three countries

The virus also travelled by air and road. A traveller from Liberia brought it to Lagos, Nigeria, in July 2014, causing 20 cases and 8 deaths before rapid contact tracing stopped it; Nigeria was declared Ebola-free in October 2014. Senegal had a single imported case and Mali a small cluster.

In the United States, a man who had travelled from Liberia died in Dallas in October 2014, and two nurses who treated him were infected and recovered. In Spain a nurse in Madrid became the first person known to be infected outside Africa, and further cases were treated in the United Kingdom and Italy. These events caused public alarm and airport screening in Western countries, but none became a wider outbreak.

Vaccine trials and the end of the epidemic

Scientists accelerated work on experimental vaccines. In 2015 a trial in Guinea known as “Ebola ça suffit” (“Ebola, that’s enough”) tested the rVSV-ZEBOV vaccine using ring vaccination, in which the contacts of each new patient, and their contacts, are vaccinated. Interim results published in July 2015 and final results in 2016 showed very high protection. The vaccine was licensed in 2019 as Ervebo and has been used in later outbreaks in the Democratic Republic of the Congo.

Liberia was first declared free of transmission in May 2015, but the virus resurfaced several times, partly because it can persist in the body fluids of some survivors for months. Sierra Leone was declared free in November 2015 and Guinea in December 2015. WHO ended the international emergency on 29 March 2016, and the end of the final flare-up in Liberia was declared on 9 June 2016.

Consequences

The epidemic killed far more people than all previous Ebola outbreaks combined. Thousands of children lost parents, and more than 17,000 survivors faced lasting health problems such as joint pain, eye disease and fatigue, as well as stigma. Because people avoided clinics and staff were diverted, deaths from malaria, measles and complications of childbirth also rose.

The economic cost was severe. The World Bank estimated that the three countries lost around 2.2 billion US dollars of economic output in 2015 alone, as mining, farming and trade were disrupted and borders closed. Schools in all three countries were shut for months.

The crisis also changed global health policy. WHO created a new Health Emergencies Programme in 2016, the African Union set up the Africa Centres for Disease Control and Prevention in 2017, and many countries invested in rapid response teams and laboratories. Experts often cite these lessons in comparisons with later outbreaks such as the COVID-19 pandemic.

By the numbers

Figures are WHO totals of confirmed, probable and suspected cases; true numbers were probably higher.

Timeline

• 2013, December: A young child falls ill and dies in Meliandou, Guinea, the earliest known case.
• 2014, 23 March: Guinea and WHO announce an outbreak of Ebola virus disease.
• 2014, May: The first cases are confirmed in Sierra Leone.
• 2014, 8 August: WHO declares a Public Health Emergency of International Concern.
• 2014, 18 September: The UN Security Council adopts Resolution 2177.
• 2014, October: Cases are diagnosed in Dallas and Madrid; Nigeria is declared Ebola-free.
• 2015, July: Interim results show the rVSV-ZEBOV vaccine is highly effective.
• 2015, November and December: Sierra Leone and then Guinea are declared free of transmission.
• 2016, 29 March: WHO ends the international emergency.
• 2016, 9 June: The end of the final flare-up in Liberia is declared.

Why it matters

The West African epidemic showed how a disease once confined to remote villages could reach crowded cities and international flights, and how weak health systems anywhere put people everywhere at risk. It also proved that rapid trials of vaccines are possible during an emergency, a lesson that shaped later preparations for new outbreaks and pandemics.