According to a statement from the Nigerian Center for Disease Control and Prevention, the outbreak continues to spread across 34 of the country’s states and the Federal Capital Territory.

The number of Lassa infections usually increases during the dry season, roughly from November to May. The disease spreads through contact with rat feces and can be transmitted from person to person.

Lassa fever is also found in a number of other African countries, such as Mali, Togo, Ghana, Liberia, and Sierra Leone. It was first identified in Nigeria in 1969.