By the end of August, the outbreak had spread to neighbouring Liberia and Sierra Leone, and the total number of probable, confirmed and suspected cases had risen to 3,685.
The CDC estimate that by the end of September, there will be around 8,000 Ebola cases - or as many as 21,000 cases if corrections for under-reporting are included - in Liberia and Sierra Leone.
And if current trends continue, "without additional interventions or changes in community behavior," these figures will rise to around 550,000 cases - or 1.4 million including under-reported cases.
The estimates assume the current conditions of disease transmission will remain unchanged. The main driver of the estimates is that in Liberia, the number of cases is doubling about every 15-20 days, and in Sierra Leone and Guinea, they are doubling around every 30-40 days.
According to the CDC, there will be up to 21,000 cases of Ebola in Liberia and Sierra Leone by the end of September.