The Association between Tuberculosis and Diphtheria

Abstract

This research investigates the now-forgotten relationship between diphtheria and tuberculosis. Historical medical reports from the 19 th century are reviewed followed by a statistical regression analysis of the relationship between the two diseases in the early 20 th century. Historical medical records show a consistent association between diphtheria and tuberculosis that can increase the likelihood and severity of either disease in a coinfection. The statistical analysis uses historical weekly public health data on reported cases in five American cities over a period of several years, finding a modest but statistically significant relationship between the two diseases. No current medical theory explains the association between diphtheria and tuberculosis. Alternative explanations are explored with a focus on how the diseases assimilate iron. In a co-infection, the effectiveness of tuberculosis at assimilating extracellular iron can lead to increased production of diphtheria toxin, worsening that disease, which may in turn exacerbate tuberculosis. Iron-dependent repressor genes connect both diseases.