SIR model consists of three compartments:
The SIR model will need two inputs that represent the two transition rates:
Basic reproduction number or basic reproduction ratio is defined as the ratio of the contact rate to the recover rate. This number reflects the number of contacts by an infected individual with others before the infected has recovered. If this number is greater than 1, the infection will spread in a population. The higher the number is, the harder to control the epidemic. For example, SARS has a basic reproduction number in the range of 2-5.
new corona virus, COVID-19, is highly contagious and caused world wide pandemic. The basic reproduction number for COVID-19 is estimated in the range of 2.13 to 3.11. The average number of days of the infection is about 14. Using that number we can input a recover rate at 0.07. Using 2.62 as the basic reproduction number, then we can input the contact rate as 0.182. Then you can input different values of the total population into the model to view the peak and number of infectious by day. By trying different population values, you can get an rough estimation of the total population infected.