The Ebola outbreak in Congo has spread from the countryside into a city, prompting fears that the disease will be increasingly difficult to control.
Health minister Oly Ilunga Kalenga confirmed a case in Mbandaka, a city of a million people about 80 miles from the area where the first cases were confirmed earlier this month.
Forty-two people have now been infected and 23 people are known to have died.
Senior World Health Organization (WHO) official Peter Salama said the spread to Mbandaka meant there was the potential for an “explosive increase” in cases.
Mr Salama, the who’s Deputy Director-General of Emergency Preparedness and response, said Mbandaka’s location on the Congo River, raised the prospect of Ebola spreading to surrounding countries such as Congo-Brazzaville and the Central African Republic as well as downstream to Kinshasa, a city of 10 million people.
The 2014-16 West Africa outbreak, which killed 11,300 people, was particularly deadly because it spread to the capital cities of Guinea, Sierra Leone and Liberia.
On Wednesday more than 4,000 doses of an experimental vaccine sent by the WHO arrived in the country with another batch expected soon.