The third-largest Ebola outbreak ever recorded is currently ripping through the Democratic Republic of Congo, with over 1,000 reported cases and 233 confirmed deaths so far. While that would be horrible enough on its own, experts are now warning that the outbreak may have started much earlier than previously believed— meaning there could be hundreds more carriers milling around, undetected.

As emergency medical professional and Ebola expert Simon Mardel told the Independent, the true scope of the outbreak could even make it the worst Ebola emergency in history. Having worked on the frontlines of three decades’ worth of outbreaks of the terrible disease, Mardel said there’s a critical gap between how many Ebola carriers health agencies have documented, and how many are actually infected.

“I think it’s safe to say it could be unprecedented,” Mardel said. “The words an epidemiologist should never want to hear are ‘unrecognized chains of transmission.'”

In order to combat outbreaks like this, Mardel notes that emergency workers need to obtain a complete picture of who’s been infected. If an outbreak reaches 100 confirmed cases, for example, the Ebola expert explains there are likely 2,000 close contacts who need to be traced and monitored. Any one of those unidentified contacts could easily be a carrier themselves — forming the “unrecognized chains” that could spell disaster.

Already, Mardel believes contact tracers “are lagging behind,” as Ebola cases have spilled beyond the DRC and into Uganda. “All the data shows that by five days, and by some markers three days, the die is cast and you can start to see who is going to die,” he told the Independent.

The nightmare scenario, he explains, would be for Ebola to reach Nigeria, Africa’s most heavily populated country. During the 2014 Ebola outbreak — believed to have begun in Guinea before spreading to Liberia, Sierra Leone, and Nigeria — was the second largest in history, claiming 11,325 lives according to the World Health Organization.

The true scope of the Ebola disaster remains to be seen. But with major funding cuts to global health programs sidelining hundreds of staffers with on-the-ground experience combating Ebola, it’s already too late to prevent a tragedy.

More on viral outbreaks: DOGE Made Drastic Cuts to a Global Vaccine Assistance Program. Now There’s a Deadly Measles Outbreak in Bangladesh