The Ebola outbreak that is spreading at unprecedented speed in Congo has not peaked yet and could be three times the current known size, according to data from authorities and Africa's top public health agency.

It is history's fastest Ebola outbreak, and the World Health Organization says it is on track to surpass the deadliest on record, which was between 2014 and 2016, with over 11,000 deaths across West Africa.

This latest outbreak has recorded 2,516 deaths out of the 5,290 confirmed cases as it rages in Congo's vast eastern region, exacerbated by an intensely mobile population, including those displaced by armed conflicts, and distrust of medical authorities.

Less than 10% of cases are currently coming from known contacts, far below the 90-95% rate when the outbreak can be said to be under control, according to Yap Boum, PhD, MPH, head of emergency preparedness and response at the Africa CDC.

Boum told reporters Thursday that under current estimates only 30% to 40% of cases have been detected.