<prompt> Prevalence is a:RateRatioPropoionNone of the above  <response>: Tools of measurement in epidemics: - Rate x 1000 10000 100000 ; a is pa of b - Ratio ab ; a is not a pa of b - Propoion x 100 ; a is pa of b Prevalence No. of all current cases of a disease at a time Estimated total population at that time X 100 Hence, Prevalence is a propoion Prevalence is NOT a Ratio: Numerator is a pa of denominator is always expressed in percentage. Incidence is rate. 