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How a Disease Spreads
Without restrictions, everyone goes out and interacts with others, thus all can possibly be infected with the virus.
A widely used technique in the epidemic domain is the SEIR model. It divides the process of people getting infective into four states: susceptible (S), exposed (E), infected (I), and resistant (R).
R0 - How many people will be infected by one patient
There are several parameters which influence the flow of people's transition from one status to another (S -> E -> I -> R), resulting in different spread speed and proportion of infected population.
Here, we can simplify the problem by understanding one parameter: the R0.
R0 is the average number of people who will catch a disease from one contagious person. It's time-varying and can help us understand the dynamics of an infectious disease.
To make it simple: as shown below, when the R0 is 3.5, one person with the disease can infect 3.5 people on average.
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