Data gathering and tracking, associated with the spread of infectious

Data gathering and tracking, associated with the spread of infectious disease in populations, is of interest to many statistical modelers.  Use Google Scholar to identify a resource discussing the topic of using mathematical models to represent the spread of disease.  

Copy and past the prompt in your response so that it is clear what you are responding to.

1) Cite your source by including the hyperlink and author / organization

2) Indicate 1 way the model may be useful for decision makers? (3-4 sentences)

3) List at least 1 variable that is measured and referenced in your model.  What does the variable measure?