<prompt> All are true for Point source epidemic except:Person-to-person transmissionClustering of cases within a short period of timeEpidemic curve rises and falls sharplyAll cases usually develop within one incubation period  <response>: EPIDEMIC:Definitions of epidemic: Occurrence of no. of cases of a disease clearly in excess of normal expectancy NENormal expectancy is derived by looking at average of no. of cases of the disease in previous 3 5 years in that geographical areaIf NE zero, even one case is considered epidemic Statistically speaking, epidemic is when no. of cases exceed twice the standard deviationNo. of cases Mean 2SD μ 2σ Occurrence of a new disease in a population as NE Zero Reoccurrence of an eliminated eradicated disease in a population as NE Zero 