<prompt> Criteria for defining polio epidemic are all except ?2 or more casesCases should occur in same localityCaused by same virus typeCases occurring during 6 month period  <response>: Ans. is d i.e., Cases occuring during 6 month period o An epidemic of polio is defined as 2 or more local cases caused by same virus type in any 4 week period. So, it has following features - i 2 or more cases of polio ii Caused by same virus type iii Within 4 week period 