The Ebola outbreak spreading in the Democratic Republic of the Congo is “likely far worse” than official figures suggest, the International Rescue Committee (IRC) warned on Monday.

The New York-based aid organization said response efforts are struggling due to delayed detection and dangerously low levels of contact tracing.

Currently, there are more than 1,000 suspected cases and more than 200 suspected deaths in the DRC, according to Congo’s Ministry of Health. So far, 282 cases and 42 deaths have been confirmed, the health ministry said.

The IRC said Ebola may have been spreading undetected since before March and potentially as long as three months before the epidemic was confirmed in mid-May.

Rachel Howard, senior technical emergency health advisor at the IRC, said only about 20% of contacts are currently being traced, meaning that health authorities are struggling to identify and isolate new chains of transmission.

At least nine travel-related case have been confirmed in Uganda as well as one death, according to the country’s health officials. The IRC is worried about cases spreading to more countries including Burundi or South Sudan, according to Howard.

“IRC teams warn that shortages of diagnostic cartridges and testing backlogs are slowing confirmation of cases, further obscuring the true spread of the outbreak,” Howard said in a statement.

She said at least six healthcare workers have died, including two doctors in recent days. Additionally, Howard said people are avoiding health facilities, which is raising fears that those affected by Ebola are remaining within communities rather than seeking treatment.

“As a result, transmission is spreading across multiple areas, and communities are losing trust in the response,” Howard said. “Strengthening local, community-based prevention and infection control should be the immediate priority to control the outbreak at the source. Without urgent funding, the situation could deteriorate rapidly.”

The current outbreak is increasingly resembling the 2018-2020 North Kivu Ebola outbreak, according to Howard. That outbreak saw more than 3,400 cases and 2,200 deaths, according to the World Health Organization.

The 2018-2020 outbreak was complicated by insecurity, population movement and community resistance, Howard noted.

However, unlike previous outbreaks, there is currently no approved vaccine available for the Ebola strain behind the current outbreak: the Bundibugyo virus.

The Coalition for Epidemic Preparedness Innovations (CEPI) announced it will “urgently accelerate” the development of three potential vaccines targeting the Bundibugyo virus.

Some public health specialists have suggested that Bundibugyo may be slightly less deadly than other Ebola strains.

The vaccines chosen are being developed by IAVI, Moderna and University of Oxford, manufactured at Serum Institute of India, and “each uses a different validated vaccine technology to maximize the likelihood of success,” CEPI said in a press release.

“The IRC is calling for urgent international support to scale up contact tracing, surveillance, laboratory testing, treatment capacity and community engagement efforts before the outbreak escalates further,” Howard said. “It is also critical to build trust with affected communities, including through survivor-led awareness and risk awareness activities.”