31,32 Cobelens and colleagues found

that a cumulative history of more than 3 months of travel to high-incidence areas increased the risk for LTBI.33 Our incidence data, however, did not show a positive association between rate of LTBI and average duration of travel. In fact, cumulative incidence of TST conversion was highest in the German military (2.9%) and in US military personnel participating in humanitarian operations (3.6%).20 Both of these groups had shorter durations of travel (<6 months) than other study populations with lower cumulative incidences, such as Peace Corps Volunteers (1.3%), most of whom serve for 27 months and many of whom live with local families in the host country. These counterintuitive results may be due to heterogeneous risk within these populations from differences in activities and exposures. Alternatively, in some settings the majority of risk for infection SB431542 in vivo may accrue early in travel. However, given the heterogeneous nature of settings, populations, and activities, and Antidiabetic Compound Library the nature of this meta-analytic

study, we were unable to determine causal relationships. Though cumulative incidence of LTBI has been documented to be higher among US forces serving in high-incidence geographic areas30,34 and on a humanitarian assistance mission among a high-risk Haitian population, some of the results of this study differ from what would be expected based on those outcomes. Edoxaban The cumulative incidence of LTBI in German and US forces deployed to Bosnia (2.9% and 2.0%, respectively) was higher than those of US forces deployed predominantly to Iraq and Afghanistan (1.7%), though the rates of TB among the local population are substantially higher in Afghanistan, and rates are as high in Iraq as they are in Bosnia.25 These differences in rates of TST conversion may, among other possible causes, be due to underreporting in US forces deployed to these regions or a lower intensity of exposure to TB among US forces.

The latter could have occurred prior to the “surge” of troops into Iraq in 2007 because the well-known danger of travel off-base from improvised explosive devices (IEDs) resulted in many US forces being isolated and kept on US military bases away from close contact with the local population. The risk of being infected by TB depends on the degree of TB exposure during travel, not simply the travel itself or its duration. TB exposure is affected by many factors, including the prevalence of TB infection in the population to which one is exposed, the presence of an infectious source, the density of droplet nuclei in the air, the duration of exposure to that air, the quality of air filtration in removing infectious droplets, whether the exposure is indoors or outdoors, and host immunological and mechanical factors.