Biostatistics & Study Design USMLE Step 1 Practice Question
A county health department follows 20,000 residents for 1 year after a contaminated water exposure. At baseline, 200 residents already have documented immunity to hepatitis A from prior infection, and 50 residents currently have acute hepatitis A. During the next year, 150 new cases of acute hepatitis A occur among residents who were previously unaffected. Which of the following is the annual incidence of acute hepatitis A in this population?
Answer choices
- A150/19,950
- B150/20,000
- C200/19,750
- D150/19,750Correct answer
- E250/20,000
- F100/19,750
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