Epidemiologic approaches to infection and immunity: the case of reactive arthritis.

PURPOSE OF REVIEW: There is significant evidence that infection and arthritis are linked, but the nature of this association is unclear. The goal of this review is to examine the case of reactive arthritis (ReA), an inflammatory arthritis with a clear infectious trigger. We will first examine the current state of knowledge of ReA epidemiology and follow it with a discussion of the epidemiologic challenges that ReA studies face.

RECENT FINDINGS: Recent studies have examined outbreaks of gastroenteritis to try and elucidate the epidemiology of ReA. Some have found higher levels of self-reported arthritis than previously thought, and others have implicated organisms such as Escherichia coli O157:H7 that were not traditionally associated with ReA. There is also evidence that the severity of initial infection may be associated with a higher relative risk of developing ReA. New population-based studies have further clarified the natural history of infection and subsequent ReA, demonstrating the power of community surveillance. Despite these findings, several methodological issues complicate the study of ReA. Problems include lack of standard diagnostic criteria, varying culture methods, selection bias and difficulties in establishing a control population.

SUMMARY: Recent studies have continued to increase our knowledge of the epidemiology of ReA. Addressing the multiple challenges that face the study of infection and arthritis will be very useful for future study.