ABSTRACT
In community-wide outbreaks of waterborne diseases there is usually little difference in rates between the two sexes and between different age groups. The strength of association is increased even more if the same strain of pathogen is isolated from ill persons and from the epidemiologically implicated water. Associations of the time that illness occurred are important patterns of a disease outbreak. Information about time of onset of illness should be available from any set of case histories that are obtained during an investigation of an outbreak, and thus an epidemic curve can be constructed as one of the bases for forming and testing hypotheses. A report of an illness or reports of illnesses of such a nature that they might be waterborne must come to the attention of a person who is concerned with either surveillance of disease or water supplies before an investigation can begin.
