Kinshasa, DRC - The number of recorded Ebola cases in the Democratic Republic of the Congo has risen to 10,060, authorities said on Tuesday, in what Africa's top health agency has described as the fastest-growing Ebola outbreak in history.

Congo's health authorities said 4,887 people have died of the disease since the outbreak was first reported in mid-May.

Cases of the highly contagious Bundibugyo variant of the virus have now also been confirmed in Kenya and Nigeria.

In Kenya, nine infections and two deaths have so far been confirmed after a patient traveled from Congo via Uganda to the capital, Nairobi.

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Nigeria confirmed its first case on October 20. The Swiss woman entered the country from Uganda. Investigations are being conducted to determine exactly where she contracted Ebola.

The patient has been evacuated to Switzerland alongside her husband, a Swiss diplomat who remains asymptomatic, according to Nigerian health officials.

Uganda recorded a total of 20 confirmed Ebola cases during the current outbreak, all traced to a patient from Congo. Two patients died.

Uganda declared its Ebola outbreak over at the end of August after no new cases had been recorded for 42 days.

The virus is transmitted through physical contact and contact with bodily fluids, and causes a highly contagious fever accompanied by diarrhea and bleeding.

The current outbreak is particularly difficult to contain as there is no vaccine to protect against the Bundibugyo variant, nor a specific treatment.

At the beginning of an infection, Bundibugyo is often mistaken for malaria due to a similarity in symptoms, which sometimes leads to delays in isolating and treating patients.

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Clinical trials to test two antiviral treatments have been under way since July.

Two further series of trials are investigating whether the Ebola vaccine Ervebo also provides protection against the Bundibugyo strain.

Ervebo is currently only authorized and recommended for use during outbreaks of the Ebola virus – formerly known as the Zaire Ebola virus.