World War I origins of the syphilis epidemic among 20th century black Americans: a biohistorical analysis.

Syphilis outbreaks and differentials have been an ongoing issue in modern preventive medicine and public health. Since the early 20th Century, a variety of approaches has been employed to explain demographic and temporal variations in the prevalence of syphilis in the U.S. Public health experts and physicians have tended to rely on case-by-case approaches to explain group-specific patterns. This study, however, shows that population-level disease dynamics cannot be ascertained from these individual-level studies. We offer a biohistorical methodology to study syphilis prevalence differentials in U.S. populations. Using historical health data, this study suggests that the social disruption brought on by World War I was the critical and unique environmental condition which ignited an epidemic of syphilis among black Americans. By establishing this beginning point for the epidemic, this study further shows the persistence of the epidemic for the next 40 years and its decline. This biohistorical methodology could be applied to the analysis of STD epidemics in other populations and regions experiencing mass exposure events.