Consider two chronic diseases A and B. Assuming in ONE year

Prevalence = The total number of PRESENT cases of a given disease in a specified population at a designated time.[ x/1000 where x is the number of cases already with the disease]

Incidence= which refers to the number of NEW cases in the population at a given time.[x/1000 where x is the number of newly infected cases]

Assuming, Prevalence and incidence of disease A and B are, Pa, Ia & Pb, Ib. What is the chance that, a person with no disease can be infected with both diseases simultaneously?

Two other confusing fact is, is the chance of person with disease A or B getting infected with the other disease same as the total incidence rate?

Is there a statistical solution to combine the incidence rate and prevalence rate of both diseases? I mean, two diseases occurring simultaneously in one individual just because of statistical chance.

Pardon me if i failed to explain the problem correctly, I am a student doctor by profession and had no clue how to approach the problem. So in short i am right where i started and it is here at the question itself. Hope to hear from some one soon. Please feel free to contact me for further clarification