WASHINGTON - A top U.S. health official who recently returned from West Africa said Monday that sustained efforts to curb the Ebola epidemic there have made a "world of difference" in helping to stabilize the region where the deadly outbreak is centered.

Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, first visited the area in August as the countries of Sierra Leone, Guinea, and Liberia were waging a losing battle against the deadly virus.

With little international support and a crumbling medical infrastructure, the countries were facing virtually unchecked virus transmission and resistance from residents who were slow to adopt disease prevention and safety measures.

If the situation had continued unabated, the CDC estimated that 550,000 to 1.4 million people in the region could have become infected by the end of January 2015.

But after months of international support, led mainly by the United States, Frieden said the situation had noticeably improved in West Africa.

The surge in manpower, funding, and resources has led to more treatment facilities and patient beds, better contact tracing to identify and isolate infected people, and better training in safe burial practices and patient care that has led to fewer infections.

The CDC projected that once 70 percent of Ebola patients were in treatment facilities or receiving proper care, the number of cases would decline about as rapidly as they had increased.

That's exactly what has happened, Frieden said. "When we got to a tipping point of isolation, care, and safe burial, there was an exponentially fast decrease in cases," he said Monday.

He said remote areas of Guinea have seen their cases plummet and more people survive their infections after France set up a treatment center. And because of their prevention efforts, Liberia - at least for now - "has the upper hand," Frieden said.

But the embattled regions still have a long way to go to shake the deadly outbreak.