As you mentioned finding the source of the infection and the denominators is paramount. As an epidemiologist, finding the source of infection to limit the spread of disease and collect statistical information for government reporting. Statistical information includes the number of those infected and those potentially affected by the disease. The denominator of an incidence proportion is the number of persons at the start of the observation period, in this case syphilis the 10 young persons with the confirmed diagnosis ("Principles of Epidemiology / Lesson 3 - Section 2," 2012). The population at risk for transmission of the disease is considered the numerator ("Principles of Epidemiology / Lesson 3 - Section 2," 2012). As the epidemiologist
