A few people might have seen the Johns Hopkins University Medical School chart on Covid-19 infection rates in different countries. They have produced many different outputs, some of them interactive world incidence models – see https://coronavirus.jhu.edu/map.html. This particular chart usefully compares some various national growth rates with straight lines representing different periods over which the number of cases might double – 1 day, 2 days, 3 days and 7 days. It’s a kind of log chart to base 2.
I’ve been beginning to simulate the outcomes for 2 input data items, in the spreadsheet here:
The spreadsheet allows you , in the last columns, to enter x and z in order to see the outcome, y.
Try it. Only change the x and z numbers, please. First input your chosen number of days (x) since the outbreak (defined at 100 cases on day zero to give a base of calculation);
Then input your chosen rate of growth of cases, expressed by an assumed number of days for doubling the cases number (z), and then:
See the output, the number of cases (y) on day x.
Of course this is only an output model, it knows nothing about the veracity of assumptions – but the numbers (y) get VERY large for small doubling periods (z).