Science, 2 June 2025

Explosive mpox outbreak in Sierra Leone overwhelms health systems

Rapid transmission through sexual networks raises fears of wider spread in the region.

Late last year, a young man traveled from Sierra Leone’s bustling capital, Freetown, to the small coastal town of Lungi, where he had sex with a sex worker. Later, he developed a fever and a headache, and then a painful rash erupted across his body, says Jia Kangbai, an epidemiologist at Njala University who interviewed the man. A nurse initially suspected malaria, but after he got back to Freetown, desperately ill, the man was diagnosed with mpox.

His was the first reported case in what soon became a massive mpox outbreak. The small West African country, population about 9 million, has seen more than 3000 cases so far. It now accounts for three-quarters of all new mpox cases in Africa, according to the Africa Centres for Disease Control and Prevention (Africa CDC).