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KINSHASA (Reuters) - Democratic Republic of Congo on Wednesday confirmed 14 new cases of Ebola virus in its eastern borderlands, the largest one-day increase since the current outbreak was declared in August.

The outbreak of the haemorrhagic fever in the eastern provinces of North Kivu and Ituri is already the second-largest in history with 713 confirmed and probable cases and 439 deaths.

It is surpassed only by the 2013-2016 outbreak in West Africa, which involved over 28,000 cases and 11,000 deaths and led to substantial investments in a vaccine and treatments for the virus.

Health officials have struggled to bring the current outbreak, Congo’s tenth since 1976, under control, largely due to widespread militia violence in eastern Congo which has hampered the response.

The health ministry said in a daily bulletin that nine of the new cases were in the health zone of Katwa, just outside Butembo, a city of several hundred thousand people near the Ugandan border that has emerged as the outbreak’s new epicenter. One other case was in Butembo.

The ministry also announced six new deaths of confirmed cases as well as the recovery of one patient.