, where C is the number of cases, C0 is the number of cases at Date0. This type of growth is sometimes called exponential and has a characteristic doubling time.
The first model fits the high growth of cases between April 27th, 2009 to May 7th, 2009 with a doubling time of 2 days..
The second model fits the growth since May 8th, 2009 with a doubling time of about 13 days.
The growth models are calculated using the exponential equation ,
where C is the number of cases, C0 is the number of cases at Date0. This type of growth is sometimes called exponential and has a characteristic doubling time.
This exponential model assumes a steady growth rate of the same type used to calculate the principle in a bank account. For example, if you have money in a bank account at 7% interest/year it will double approximately every 10 years.
The current doubling times corresponds to an approximate interest rate of 5-7%/day which is much faster than any type of financial investment that you have ever had (unless you invested with Madoff. Ha!).
At the current growth rate, we would expect the number of cases in the world to exceed one million by September 1st, 2009. Hopefully, things will slow down further with the onset of summer.
Despite what the newspapers say, it would be a good idea to excercise caution if you are not sick and to quarantine yourself if you do get the swine flu. These are my recommendations not as a doctor but as someone who has respect for the exponential function.