The International Rescue Committee, a nonprofit global aid group, posted a warning Monday that the current Ebola outbreak in the Democratic Republic of Congo could have been spreading for three months before any cases were detected.

​In the press release published by IRC on Monday, the group cited “delayed detection and slow contact tracing” as reasons for the virus’s undetected spread. The true scale of infections is likely far higher than that reported by other official sources, according to the group.