Problem with space-time clusters - deal only with clusters of cases and do not take into account the various concentrations of the population in the communities where the cases appear.

Age - infectious disease in childhood (mumps); Trisomy 21 in children with older mothers;
Gender - Kuru - slow virus from cannibalism. Women in West Guinea were at greater risk for this because they prepared the bodies for funeral and often consumed the uncooked brains.

Race & Ethnicity - Tay-Sachs, sickle-cell anemia, BRCA gene with Ashkenazi women.
D. latum tapeworm infestation of Jewish housewives in 1940s - from sampling uncooked gefilte fish.