A yet-unidentified illness has killed 53 people and potentially infected hundreds more in the Democratic Republic of the Congo. The World Health Organization is investigating the outbreak.

The WHO Africa office said the quick progression from sickness to death in Boloko is a key concern, along with the high number of deaths in Bomate. Congo’s Ministry of Health said about 80% of the patients share similar symptoms including fever, chills, body aches and diarrhea.

A mysterious disease outbreak in the Democratic Republic of Congo has claimed over 50 lives, with symptoms resembling haemorrhagic fever. The illness, which reportedly spreads rapidly and leads to death within 48 hours,