Poliovirus has been found in samples from Bajul, the capital of the West African country of Gambia, and Kotu, a seaside resort area.
This was stated by the Minister of Health Ahmadu Lamin Samateh.
The spread of the deadly virus in a country of about 2 million people, he said, has forced the government to launch a vaccination campaign to stop the epidemic.
Samateh added that the campaigns target all children under the age of five.
In addition to the Gambia, poliovirus has been detected in Africa, Uganda, Benin, Burkina Faso, Cameroon, Ethiopia, Mali, Nigeria, Chad and Sudan.