<prompt> The time interval between the primary and secondary case is :Serial intervalGeneration timeMedian Incubation periodSecondary attack rate  <response>: Ans. is a i.e. Serial interval Serial intervalThe gap in time between the onset of the primary case and the secondary case is called the serial interval.Generation time is the interval of time between receipt of infection by a host and maximal infectivity of that host.Median incubation periodis the time required for 50 percent of the cases to occur following exposure. 