Or how long does it take for the poison to develop symptoms after infection: generally three to six days, but the period may be up to ten days. The period varies with the virulence of the poison. The germs, however, remain active outside a host for a long time. An instance has been reported, in which a man, after handling some ropes which 20 years previously had been used in the burial of plague corpses, took the disease and died of it.