Caption: continous source epidemic
Text: An epidemic in which the causal agent (e.g. polluted drinking water, spoiled food) is infecting people who come into contact with it, over an extended period of time, i.e., over more than one incubation period. The incubation period for cholera is 1-3 days, but the Broad Street epidemic extended over a period of 3-4 weeks, so there was a "continuous source" of cholera exposure.