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 Q*n* be the quantity on the *nth* day, and C be some constant value. then

In a geometric progression, **Q***n+1* = Q*n* * C, such as (when C = 2)

**00002, 00004, 00008, 00016, 00032, ...**

In an exponential progression, **Q***n+1* = Q*n* ** 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.