Lassa fever: West Africa

The most severely affected countries are in the region known as the Manu River Union ( Liberia, Sierra Leone and Guinea) and Nigeria. However, there is evidence of Lassa virus infection in other African countries, demonstrated either by sporadic human cases, or by rodent or human sero-prevalence studies.

• See other maps for more detail and explanation - Africa, Guinea, Liberia, Nigeria, Sierra Leone

The areas of Lassa fever endemicity are not limited by political or country boundaries but rather by geographical areas. As seen in the map below, eastern Sierra Leone, southwestern Guinea, and northwestern Liberia, all hyperendemic for Lassa, are adjacent to each other.

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(Based on United Nations Map No. 4242, February 2005)

Last reviewed: 14 February 2012