Perhaps the terms are used differently in different parts of the world. Hmm. Not so easy to show what I mean given Slashdot's limited HTML subset. Here goes:
When I say geometric, I mean each successive term is the same multiple of its previous term.
When I say exponential, I mean each successive term is the previous term raised to some power.
Let Qn be the quantity on the nth day, and C be some constant value. then
In a geometric progression, Qn+1 = Qn * C, such as (when C = 2)
00002, 00004, 00008, 00016, 00032, ...
In an exponential progression, Qn+1 = Qn ** C, such as (again when C = 2)
00002, 00004, 00016, 00256, 65536, ...
I'm using leading zeroes to keep the digits nicely lined up, so each nth term is in the same column in both series.
With regard to the ebola situation, it might well be that the geometric constant will be a higher value than 2 while the exponential constant is a smaller value than 2. Say the geometric increases at 3 while the exponential increases at 1.7. Then (rounding to nearest whole number)
0000003, 0000009, 0000027, 0000081, 0000243, 0000729, 002187, ... (geometric, C=3)
0000002, 0000002, 0000005, 0000014, 0000084, 0001871, 365155, ... (exponential, C=1.7)
I think that shows how dismal Malthus' mathematics is. We need a breakthrough, like the impact the internal combustion engine had on food crops. But you just can't plan on miracles happening when you need them. That isn't part of the human condition.