Unpacking the 'black box' of total pathogen burden: is number or type of pathogens most predictive of all-cause mortality in the United States?

A 'black box' paradigm has prevailed in which researchers have focused on the association between the total number of pathogens for which individuals are seropositive (i.e. total pathogen burden) and various chronic diseases, while largely ignoring the role that seropositivity for specific combinations of pathogens may play in the aetiology of such outcomes and consequently mortality. We examined the association between total pathogen burden as well as specific pathogen combinations and all-cause mortality in the United States. Data were from individuals aged ⩾25 years tested for cytomegalovirus (CMV), herpes simplex virus (HSV)-1, HSV-2 and Helicobacter pylori, with mortality follow-up to 31 December 2006 in the National Health and Nutrition Examination Survey (NHANES) III (N = 6522). We did not observe a statistically significant graded relationship between total pathogen burden level and all-cause mortality. Furthermore, compared to those seronegative for all four pathogens, the greatest statistically significant rate of all-cause mortality was for those CMV+/HSV-2+ (hazard ratio 1·95, 95% confidence interval 1·13-3·35) adjusting for age, gender, race/ethnicity, education level, body mass index (kg/m2) and smoking status. Interventions targeting prevention or treatment of particular pathogens may be more effective for reducing mortality than those focused solely on reducing overall pathogen burden.