Ebola: Mapping the outbreak Published duration 14 January 2016

The Ebola outbreak in West Africa was first reported in March 2014, and rapidly became the deadliest occurrence of the disease since its discovery in 1976.

In fact, the epidemic killed five times more than all other known Ebola outbreaks combined.

More than 21 months on from the first confirmed case recorded on 23 March 2014, 11,315 people have been reported as having died from the disease in six countries; Liberia, Guinea, Sierra Leone, Nigeria, the US and Mali.

The total number of reported cases is about 28,637.

But on 13 January, 2016, the World Health Organisation declared the last of the countries affected, Liberia, to be Ebola-free.

The World Health Organization (WHO) admits the figures are underestimates, given the difficulty collecting the data.

There needs to be 42 days without any new cases for a country to be declared Ebola-free.

The outbreaks in Nigeria and Senegal were declared officially over by the WHO in October 2014. Sierra Leone and Guinea both had much larger outbreaks and it took a little longer. Sierra Leone was declared Ebola-free on 7 November 2015, Guinea followed in December.

Liberia has been the worst-hit, with more than 4,800 dead and 10,672 becoming infected. The WHO said that at the peak of transmission, during August and September 2014, Liberia was reporting between 300 and 400 new cases every week.

The epidemic seemed to abate and the outbreak in Liberia was declared over on 9 May 2015 - only to re-emerge seven weeks later when a 17-year-old man died from the disease and more cases were reported. The same happened in September, which is why the latest declaration of Liberia being Ebola-free, while welcome, should be treated with caution, say correspondents.

The WHO has warned that West Africa may see flare-ups of the virus.

How the virus spread

In March, hospital staff alerted Guinea's Ministry of Health and then medical charity Medecins Sans Frontieres (MSF). They reported a mysterious disease in the south-eastern regions of Gueckedou, Macenta, Nzerekore, and Kissidougou.

It caused fever, diarrhoea and vomiting. It also had a high death rate. Of the first 86 cases, 59 people died.

The WHO later confirmed the disease as Ebola.

Ebola death toll

image copyright AP

Ebola outbreak: Key stories

Disease spreads

The Gueckedou prefecture in Guinea, where the outbreak started, is a major regional trading centre and, by the end of March, Ebola had crossed the border into Liberia. It was confirmed in Sierra Leone in May.

In June, MSF described the Ebola outbreak as out of control

Nigeria had its first case of the disease in July and, in the same month, two leading doctors died from Ebola in Liberia and Sierra Leone

In August, the United Nations health agency declared an "international public health emergency", saying that a co-ordinated response was essential to halt the spread of the virus.

Senegal reported its first case of Ebola on 29 August. A young man from Guinea had travelled to Senegal despite having been infected with the virus, officials said.

By September, WHO director general Margaret Chan said the number of patients was "moving far faster than the capacity to manage them".

Director of the Centers for Disease Control and Prevention (CDC) in the US, Thomas Frieden, said in October that the Ebola outbreak in West Africa was unlike anything since the emergence of HIV/Aids. But Senegal managed to halt transmissions by mid October.

Authorities in Mali confirmed the death of the country's first Ebola patient, a two-year-old girl, on 25 October. The girl had travelled hundreds of kilometres by bus from Guinea through Mali showing symptoms of the disease, the WHO said.

An infected Islamic preacher from Guinea, who was initially diagnosed with a kidney problem, was treated at a clinic in Bamako. The preacher died a few days after entering the country.

Two health workers who cared for the preacher also died after contracting the virus. In total, Mali recorded six deaths from Ebola. By January 2015 however, the country was declared ebola-free.

Ebola outside West Africa

*In all but three cases the patient was infected with Ebola while in West Africa. Infection outside Africa has been restricted to health workers in Madrid and in Dallas. DR Congo also reported a separate outbreak of an unrelated strain of Ebola.

The first case of the deadly virus diagnosed on US soil was announced on 1 October . Thomas Eric Duncan, 42, who contracted the virus in Liberia before travelling to the US, died on 8 October.

He had not displayed symptoms of the disease until 24 September, five days after his arrival. Other people with whom he came into contact are being monitored for symptoms.

Two medical workers in Dallas, Texas, who treated Duncan tested positive for Ebola since his death but have both recovered. The second death on US soil was surgeon Martin Salia, from Sierra Leone. He was flown back to the United States in November and treated for Ebola at a hospital in Nebraska. But Dr Salia, who had US residency and was married to an American, died a short time later.

Spanish nurse Teresa Romero was the first person to contract the virus outside West Africa. She was part of a team of about 30 staff at the Carlos II hospital in Madrid looking after two missionaries who returned from Liberia and Sierra Leone after becoming infected.

Germany, Norway, France, Italy, Switzerland and the UK have all treated patients who contracted the virus in West Africa.

2014 outbreak in context

Ebola was first identified in 1976 and occurs in regions of sub-Saharan Africa. There are normally fewer than 500 cases reported each year, and no cases were reported at all between 1979 and 1994.

In August 2014, the WHO confirmed a separate outbreak of Ebola in the Democratic Republic of Congo. By the beginning of October there had been 70 cases reported and 43 deaths.

However, the outbreak in DR Congo was a different strain of the virus and unrelated to the epidemic in West Africa, which now dwarfs all previous outbreaks.