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Ebola: Tracking the Outbreak

Ebola has infected over 24,000 people and caused more than 10,000 deaths in West Africa since March 2014. One year later the outbreak has slowed but new cases continue to be reported each week. No significant decline in new cases has been seen since late January, but the geographical extent of the outbreak has decreased, allowing health officials to focus their efforts.

Data as of March 18, 2015

The deadliest species

The ongoing outbreak has caused more cases and deaths than all other Ebola outbreaks combined. Since the first known cases in Africa in 1976, three of the five species of the Ebolavirus genus—the Sudan, Bundibugyo, and Zaire species—have accounted for almost all cases. The Zaire species, responsible for the current outbreak, is the deadliest strain of the disease. A fourth species (Taï Forest) caused one nonfatal case in Côte d'Ivoire in 1994. A fifth (Reston) has not yet been transmitted to humans.

Darker-colored circles indicate deaths and lighter-colored circles indicate cases.

The current situation

Three West African countries are still battling the outbreak: Liberia, Guinea, and Sierra Leone. The outbreaks in Senegal and Nigeria were declared over in October; Mali also recently became Ebola free. Unlike previous outbreaks that primarily occurred in remote villages, this one includes urban areas. The first case occurred in Guinea in early December 2013, but scientists didn’t identify Ebola as the culprit until March 2014. A week-by-week breakdown shows the disease ramping up in mid-August and slowing in January.

Weekly charts show case numbers from the World Health Organization (WHO) situation reports and patient databases. The databases are generally more accurate than the reports but are less complete for recent weeks.The WHO releases situation reports approximately every week with the latest data available on confirmed, probable, and suspected cases.

Total ebola cases by week (global)

Patient

Situation

Sierra Leone

New cases have been reported in the districts near Freetown, the capital.

Guinea

Since late February, no new cases have been reported.

Liberia

New cases are clustered in and around the capital Conakry.

Sources: World Health Organization

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