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Cross-border solutions needed to address tuberculosis in migrating populations.

THE ‘PERFECT STORM’ of 10.4 million tuberculosis (TB) cases globally, 1.4 million TB deaths globally,1 and 244 million migrants crossing international borders annually,2 continues to generate attention across the world. Whether it’s from news headlines or from country surveillance reports, epidemiologists and policy makers are increasingly aware of the challenges of addressing TB in migrating populations. With this awareness, one fact is clear: World Health Organization (WHO) targets for TB elimination cannot be met without addressing TB in mobile populations.3 In this issue, van Aart et al. add to our understanding of TB in migrating populations in the Netherlands.4 They find that a migrant population originating from a high TB incidence area (Somalia) experiences a time lag in TB diagnosis of 17 months after arrival, while populations from lower incidence areas (Turkey and Morocco) do not. Their findings help elucidate a key principle about the burden of TB in migrating populations. While there is much concern about the potential for TB importation when migrants arrive in new countries, there is less understanding of the long-term TB burden after they have lived in their destination countries for several years. This research, which involves the application of sophisticated modeling techniques, helps public health professionals and policy makers to better understand the epidemiologic features of TB in mobile populations, thus informing best practices for TB control in these populations. Evaluating the impact of TB control strategies across the full spectrum of migration is important to reduce the global TB burden. Showing that elevated TB diagnosis rates can persist for key populations after arrival in the Netherlands underscores the fact that interventions must be developed to reduce the long-term burden of latent Mycobacterium tuberculosis infection (LTBI). The research also highlights the importance of developing interventions in communities where the migrants originated, so that risk of TB infection and transmission can be lowered prior to migration. Indeed, the WHO End TB Strategy calls for ‘addressing the health issues of migrants and strengthening cross-border collaboration’.3 A previous study showed that bolstering TB control strategies in source country populations will yield a greater long-term return on investment than improving premigration screening algorithms to prevent importation.5 In this context, community-based TB control efforts among Somali groups in Africa will ultimately have a beneficial effect on reducing TB among Somalis in the Netherlands. If the burden of TB can be lowered in source communities, fewer people in those communities will become infected, the pressure on screening programs to detect cases will be lowered (whether screening occurs before a migrant’s departure or immediately after arrival), and fewer cases will be diagnosed from reactivation of LTBI. Moreover, as many of the WHO high TB burden countries are also among the world’s leading source countries for migrants, building capacity to address TB in source communities would contribute to global elimination efforts.1,2 The findings from these analyses and others should be used to help develop strategies to address TB in mobile populations across the spectrum of their migration pathways. TB is a disease that does not respect national borders; the solutions to stopping the epidemic must thus also be cross-border, collaborative, and multi-national.