Abstract
Tuberculosis (TB) causes significant morbidity and mortality in high-income countries with foreign-born individuals bearing a disproportionate burden of the overall TB case burden in these countries. In this review of tuberculosis and migration we discuss the impact of migration on the epidemiology of TB in low burden countries, describe the various screening strategies to address this issue, review the yield and cost-effectiveness of these programs and describe the gaps in knowledge as well as possible future solutions.The reasons for the TB burden in the migrant population are likely to be the reactivation of remotely-acquired latent tuberculosis infection (LTBI) following migration from low/intermediate-income high TB burden settings to high-income, low TB burden countries.TB control in high-income countries has historically focused on the early identification and treatment of active TB with accompanying contact-tracing. In the face of the TB case-load in migrant populations, however, there is ongoing discussion about how best to identify TB in migrant populations. In general, countries have generally focused on two methods: identification of active TB (either at/post-arrival or increasingly pre-arrival in countries of origin) and secondly, conditionally supported by WHO guidance, through identifying LTBI in migrants from high TB burden countries. Although health-economic analyses have shown that TB control in high income settings would benefit from providing targeted LTBI screening and treatment to certain migrants from high TB burden countries, implementation issues and barriers such as sub-optimal treatment completion will need to be addressed to ensure program efficacy.
Highlights
In this review we first analyse the burden of tuberculosis (TB) in foreign-born, migrant populations before going on to discuss the drivers of the current TB epidemiology in these populations focusing on migration patterns, the importance of reactivation of latent tuberculosis infection as compared to the burden of imported active TB and molecular genotyping data underpinning these studies
Targeted pre-arrival screening for active TB and post arrival screening for latent tuberculosis infection in migrants from intermediate/high TB burden settings may provide the most cost-effective solution
Aldridge and colleagues undertook a detailed systematic review and meta-analysis on the yields of active TB through prearrival screening. They found that the overall yield for culture positive active TB was 0.22 % (219 cases/100,000) [71]; the yield for culture positive TB increased with increasing TB prevalence in country of origin [71] suggesting that setting an incidence threshold for pre-arrival screening of migrants may be needed to ensure costeffective use of resources
Summary
In this review (see Table 1) we first analyse the burden of tuberculosis (TB) in foreign-born, migrant populations before going on to discuss the drivers of the current TB epidemiology in these populations focusing on migration patterns, the importance of reactivation of latent tuberculosis infection as compared to the burden of imported active TB and molecular genotyping data underpinning these studies. Drilling down further into the patterns TB notifications in the foreign-born population in high-income countries reveals information about key risk groups with the highest incidence and risk of active TB following migration: migrants from Asia and Africa where the burden of TB is moderate/high, recent migrants (within 5 years of arrival), refugees and individuals with comorbidities (such as HIV infection and diabetes mellitus) [7, 9, 10, 12, 13]. In high-income countries this is complemented by the contact-tracing of household contacts of smear-positive cases with the overall aim of reducing onward transmission This method of TB control does not fully address the potential source of reactivation of remotely acquired LTBI progressing to active TB disease – such as that seen in migrants.
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