Question

On August 21, 2009, the World Health Organization announced its prediction that the number of new cases of H1N1 (swine flu) virus would double every 4 days for several months. As of July 27, 2009, the number of new cases was 15,784. Determine the instantaneous growth rate for the virus (rounded to the nearest ten-thousandths).

Answer 1

growth rate = 0.1733 per day, or 17.33% per day

Explanation:

Since the doubling time is 4 days, the growth factor over a period of t days is ...

2^(t/4)

Then the growth factor for 1 day is

2^(1/4) ≈ 1.189207

The instantaneous growth rate is the natural log of this:

ln(1.189207) ≈ 0.1733 . . . per day