Meltzer and his team built a model that estimates how many new cases the region might see, depending on when certain levels of intervention are offered. The model is based on data from up to late August — before American and British military aid was pledged, and before new Ebola treatment units opened in Liberia — and like any projection, it offers a range, not a single number.

On the low end, the study said, the region would see 550,000 more Ebola cases if nothing changed. On the highest side of the high end, it estimated 1.4 million.

But even Meltzer says actually reaching 1.4 million cases is unlikely — and not just because the dismally slow global response is finally starting to speed up.

“We’re getting hints of data, though it’s not been confirmed, that people are changing their behavior toward less risk of onward transmission,” Meltzer said.