Propagative epidemic, transmission is -

.a propagated epidemic is usually of infectious origin.its mode of transmission is from person to person always.the epidemic usually shows a gradual rise and tails off over a much longer time.transmission continues untill the number of susceptibles depleted.the speed of spread depends upon herd immunity ,oppounities for contact and secondary attacks rates.occur commonly in aggregated populations. ref:park&;s textbook,22 nd ed,pg 63