The SIS Model
Some infections, for example the group of those responsible for the common cold, do not confer any long lasting immunity. Such infections do not have a recovered state and individuals become susceptible again after infection.
We have the model:
Note that denoting with N the total population it holds that: it follows that:
i.e. the dynamics of infectious is ruled by a logistic equation, so that :
Read more about this topic: Compartmental Models In Epidemiology
Famous quotes containing the word model:
“When Titian was mixing brown madder,
His model was posed up a ladder.
Said Titian, “That position
Calls for coition,”
So he lept up the ladder and had her.”
—Anonymous.