Question

An epidemiologist is investigating two suspected risk factors for a deadly disease (“wasting disease”). One of the potential risk factors is infection by virus A, while the other potential risk factor is having a mutation in a gene on chromosome 10. 6,500 participants were selected for the 2 year study. Of those participants, 500 were infected by virus A but did not have the genetic mutation, 750 had the mutation but did not have the virus, and 400 had both the virus and the genetic mutation. Of those with virus A infection but not the genetic mutation, 150 acquired wasting disease. Of those with the genetic mutation but not with virus A infection, 300 acquired wasting disease. Of those with both the genetic mutation and an infection with virus A, 20 acquired wasting disease. Finally, 2,425 of those with neither the virus nor the genetic mutation acquired the disease during the study period.

What is the risk (incidence per 1000 people per year) of acquiring the disease among those with both virus A and the genetic mutation?

What is the relative risk for having both the genetic mutation and virus A, using those who have neither the genetic mutation nor virus A as the comparison group (denominator)?

What is the relative risk for having only virus A (and not the genetic mutation), using those who have neither the genetic mutation nor virus A as the comparison group?

Answer 1