SI model

The SI model is a simple way to understand how a contagious disease spreads through a population. It divides people into two groups: those who are susceptible (healthy but can catch the disease) and those who are infectious (currently sick and able to spread it). Once someone becomes infected, they stay infectious for the duration of the outbreak. The model predicts that over time, susceptible individuals become infected, leading to a steady increase in infectious cases until everyone who can be infected has been, resulting in the entire population eventually being infected.