Suppose that you began a one-year study of tuberculosis (TB) in St. Petersburg on January 1st, 2018. You enrolled 200 residents in your study and checked on their TB status on a monthly basis. At the start of your study on January 1st, you screened all 200 residents. Upon screening, you found that 10 of the healthy residents were immigrants who were vaccinated for TB and so were not at risk. Another 10 residents already had existing cases of TB on January 1st. On February 1st, two residents developed TB. On April 1st, three more residents developed TB. On July 1st, three of the residents who had existing TB on January 1st died from their disease. The study ended on December 31, 2018. Assume that once a person gets TB, they have it for the duration of the study, and assume that all remaining residents stayed healthy and were not lost to follow-up. 1. What was the prevalence of TB in the screen community on April 1st?
2. What was the cumulative incidence of TB over the year? Calculate and interpret this finding.
3. What was the case-fatality rate among residents with TB over the course of the year?
4. Calculate and interpret.