Liberia's Deputy Health Minister and Chief Medical Officer Francis Kateh told the BBC that more than 90 cases have been reported across the country; but 25, including the 21 deaths, have so far been confirmed.

Lassa fever is an animal-borne, or zoonotic, acute viral illness. It is endemic in parts of West Africa including Sierra Leone, Liberia, Guinea and Nigeria.

Neighboring countries are also at risk, according to the US Centers for Disease Control. In Liberia it is spread mainly by rats and cockroaches.

Mr Kateh says even though Lassa fever has been an usual health problem in some parts of Liberia for a very long time, authorities see the current outbreak as a matter of serious concern because it is happening at a time of the year when it is not expected.

Healthcare delivery is still almost non-existent in most of Liberia with hospitals and clinics lacking drugs and basic things needed to function.

A lack of political will and finances are also to blame.