<prompt> A population of 100000 is under surveillance during an year. 100 cases were positive for malarial thick smear. What is the annual parasite index -1 per 10002 per 100010 per 100020 per 1000  <response>: Ans. is a i.e., 1 per 1000 Annual Parasite Incidence confirmed cases during one yearpopulation under surveillancee x 1000 Population under surveillance 100000 Confirmed cases 100API 100---100,000x 1000 1 So, API is 1 per 1000 population. 