Emergencies preparedness, response

Origins of the 2014 Ebola epidemic

One year into the Ebola epidemic. January 2015

A "mysterious" disease began silently spreading in a small village in Guinea on 26 December 2013 but was not identified as Ebola until 21 March 2014.

WHO mobile lab scientists at the crossing point between Guinea and Sierra Leone.
WHO/Saffea Gborie

Retrospective studies conducted by WHO staff and Guinean health officials identified the index case in West Africa’s Ebola epidemic as an 18-month-old boy who lived in Meliandou, Guinea. The boy developed an illness characterized by fever, black stools, and vomiting on 26 December 2013 and died two days later. The exact source of his infection has not been identified but likely involved contact with wild animals.

The remote and sparsely populated village of Meliandou, with only 31 households, is located in Gueckedou District in what is known as the Forest Region. Much of the surrounding forest area has, however, been destroyed by foreign mining and timber operations.

Some evidence suggests that the resulting forest loss, estimated at more than 80%, brought potentially infected wild animals, and the bat species thought to be the virus’ natural reservoir, into closer contact with human settlements. Prior to symptom onset, the child was seen playing in his backyard near a hollow tree heavily infested with bats.

"You have to know Ebola to fight Ebola. Mobilize your people."

Dr Clement, WHO, Liberia

By the second week of January 2014, several members of the boy’s immediate family had developed a similar illness followed by rapid death. The same was true for several midwives, traditional healers, and staff at a hospital in the city of Gueckedou who treated them.

During the following week, members of the boy’s extended family, who attended funerals or took care of ill relatives, also fell sick and died. By then, the virus had spread to four sub-districts via additional transmission chains. A pattern of unprotected exposure, more cases and deaths, more funerals, and further spread had been established.

The first investigations: cholera?

The first alert was raised on 24 January, when the head of the Meliandou health post informed district health officials of five cases of severe diarrhoea with a rapidly fatal outcome. That alert prompted an investigation the next day in Meliandou by a small team of local health officials. The reported symptoms, including diarrhoea, vomiting, and severe dehydration, appeared similar to those of cholera, one of the area’s many endemic infectious diseases. However, no firm conclusions could be reached.

A second larger team, including staff from Médecins Sans Frontières (MSF) travelled to Meliandou on 27 January. Microscopic examination of patient samples showed bacteria, again supporting the conclusion that the unknown disease was likely cholera. Following the team’s visit, other deaths occurred but were neither reported nor investigated.

On 1 February, the virus was carried into the capital, Conakry, by an infected member of the boy’s extended family. He died four days later at a hospital where, as doctors had no reason to suspect Ebola, no measures were taken to protect staff and other patients. As the month progressed, cases spread to the prefectures of Macenta, Baladou, Nzerekore, and Farako as well as to several villages and cities along the routes to these destinations.

Alert, investigation and identification of the Ebola virus

The Ministry of Health issued its first alert to the unidentified disease on 13 March 2014. On that same day, staff at WHO’s Regional Office for Africa (AFRO) formally opened an Emergency Management System event for a disease suspected to be Lassa fever.

A major investigation, involving staff from the Ministry of Health, WHO AFRO, and MSF, took place from 14 to 25 March, involving site visits to Kissidougou, Macenta, Gueckedou City and Nzerekore. That investigation found epidemiological links among outbreaks previously not known to be connected and identified Gueckedou City as the epicentre for transmission of a disease that still had no known cause.

On 21 March, the Institut Pasteur in Lyon, France, a WHO Collaborating Centre, confirmed that the causative agent was a filovirus, narrowing the diagnosis down to either Ebola virus disease or Marburg haemorrhagic fever.

The next day, the laboratory confirmed that the causative agent was the Zaire species, the most lethal virus in the Ebola family. That same day, the government alerted WHO to what was described as a “rapidly evolving” outbreak of Ebola virus disease. When WHO publicly announced the outbreak on its website on 23 March, 49 cases and 29 deaths were officially reported.