More than 7,000 Ebola cases have been recorded in the Democratic Republic of the Congo’s (DRC) worst outbreak of the deadly disease, according to figures from Congolese authorities.

The DRC officially detected the latest outbreak in mid-May, but experts suspect it had been spreading under the radar for weeks before.

Of the 7,022 registered cases, 3,398 people have died, according to DRC authorities. Currently, 837 people are in isolation or receiving treatment.

The outbreak of the rare Bundibugyo virus, DRC’s 17th Ebola epidemic, began in the northeastern Ituri province.