More than 2,000 people have died among confirmed cases in Congo’s Ebola outbreak, which is spreading at the fastest pace recorded in the country, according to government data released Tuesday.

The outbreak has recorded 4,381 confirmed cases and 2,011 deaths, while 704 patients are hospitalized or in isolation. The figures come less than three months after authorities declared the outbreak May 15.

The pace of deaths has accelerated sharply. It took about nine weeks for the outbreak to reach 1,000 deaths, but only about three additional weeks to record another 1,000, highlighting the difficulties health workers face reaching remote communities and containing transmission.

The outbreak is being caused by the Bundibugyo virus, a relatively rare species of ebolavirus for which there are no approved vaccines or specific treatments.

The World Health Organization (WHO) said Monday that genomic and epidemiological evidence indicates the virus began circulating in February, months before authorities detected it.