One of the largest groups fighting Ebola in West Africa is warning the world not to slow down its response to the disease even as the number of cases continues to plummet across the region.

Doctors Without Borders is now treating only 50 patients out of the 5,000 that have entered its eight treatment centers. But its leader declared Monday that the organization is not letting down its guard.

“While this is a promising development, [Doctors Without Borders] cautions that a loss of vigilance now would jeopardize the progress made in stemming the epidemic,” the agency wrote in a statement.

Across the region, cases have dropped significantly.

Only five cases of Ebola remain in Liberia out of more than 8,400 cases reported there. In Sierra Leone, cases have dropped to their lowest levels since August. Caseloads have also decreased in Guinea, though “hotspots” for the disease remain.

The group is still pressing for stronger surveillance, better contact-tracing and more accurate education in some of the worst-affected areas, such as rural areas of Guinea, where the epidemic first began.