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The number of Ebola cases in Liberia and Sierra Leone could rise to between 550,000 and 1.4 million by January if there are no "additional interventions or changes in community behavior," the Centers for Disease Control and Prevention said in a report Tuesday. The estimate was derived from a new forecasting tool developed by the CDC, CNN reported.

The range of estimated cases -- from 550,000 to 1.4 million -- is wide because experts suspect the current count is highly under-reported. The official death toll from Ebola in West Africa has climbed to more than 2,800 in six months, with 5,800 cases confirmed as of Monday, the World Health Organization said.

But the CDC estimates that if 70% of people with Ebola are properly cared for in medical facilities, the epidemic could decrease and eventually end.

In a press conference Tuesday, CDC Director Tom Frieden cautioned that this model is based on older data from August. The numbers are not projections, but "scenarios." The model does not take into account President Obama's announcement that the U.S. is sending troops and extra medical equipment to the area. Nor does it take into account the additional help from other countries promised.

What the model does suggests, he said, is that the current surge of help can "break the back of the epidemic" and is "exactly what's needed" to end it. He said he is now "confident the most dire predictions will not come to pass."

The cautionary tale this data does tell, he said is that there would be an "enormous cost" if help is delayed.