The number of people infected with Ebola in Congo-Kinshasa could be two to four times higher than the official figure, the World Health Organization (WHO) has said.

According to the country’s health authority, 719 people have died from Ebola and nearly 2,000 have been confirmed infected.

But WHO’s head of emergencies, Chikwe Ihekweazu, said on Monday that the organization’s analyses indicate that “the scale of the outbreak is at least two to four times larger than the number of cases we have identified.”

The outbreak in Congo-Kinshasa started in May and has affected four provinces. The hardest hit is Ituri province in the northeast of the country.

The current outbreak is driven by the Bundibugyo variant, for which there is no vaccine or specific treatment.