Question

In the following description of a setting for a model of the spread of an infectious disease, healthy people in the population are called susceptibles and people with the disease are called infectives. During a period there is a 0.05 probability that a given infective will encounter a particular susceptible. If an infective encounters a susceptible, there is a 0.5 probability that the susceptible will contract the disease. Each infective at the beginning of a period has a 0.1 probability of dying by the end of the period. Select the least accurate statement regarding elements of a model for this setting.

Answer 1

Explanation:

If a person becomes immune to a disease after recovering from it, and births and deaths in the population are not taken into account, then the percentage of persons susceptible to becoming infected with the disease S(t), the percentage of people in the population infected with the disease I(t), and the percentage of people in the population recovered and immune to the disease R(t) can be modeled by the system

Because S(t) + I(t) + R(t) = 1, once we know S and I, we can compute R with R(t) = 1 − S(t) − I(t). This model is called an SIR model without vital dynamics because once a person has had the disease, the person becomes immune to the disease, and because births and deaths are not taken into consideration. This model might be used to model diseases that are epidemic to a population: those diseases that persist in a population for short periods of time (less than 1 year). Such diseases typically include influenza, measles, rubella, and chicken pox