The area is declared free of epidemic:
Epidemic: Number of cases of a disease clearly in excess of normal frequency. An area is declared free of epidemic; if on search , no new cases are repoed for 'twice the incubation period of the disease since the occurrence of last case'.
Till last secondary case recovers
No new case repoed for the incubation period of disease since the last case
No new case repoed for twice the incubation period of disease since the last case
No new case repoed for six months since the last case
Time Distribution, Epidemics