High Rates ofMycobacterium tuberculosisamong Socially Marginalized Immigrants in Low-Incidence Area, 1991–2010, Italy

Iacopo Baussano,Manish Pareek,Ajit Lalvani,Silvio Mercadante,Massimiliano Bugiani

doi:10.3201/eid1909.120200

Iacopo Baussano, Manish Pareek + Show 3 more

Open Access

https://doi.org/10.3201/eid1909.120200

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Abstract

Migration from low- and middle-income countries to high-income countries increasingly determines the severity of tuberculosis (TB) cases in the adopted country. Socially marginalized groups, about whom little is known, may account for a reservoir of TB among the immigrant populations. We investigated the rates of and risk factors for Mycobacterium tuberculosis transmission, infection, and disease in a cohort of 27,358 socially marginalized immigrants who were systematically screened (1991–2010) in an area of Italy with low TB incidence. Overall TB and latent TB infection prevalence and annual tuberculin skin testing conversion rates (i.e., incidence of new infection) were 2.7%, 34.6%, and 1.7%, respectively. Prevalence of both TB and latent TB infection and incidence of infection increased as a function of the estimated TB incidence in the immigrants’ countries of origin. Annual infection incidence decreased with time elapsed since immigration. These findings have implications for control policy and immigrant screening in countries with a low prevalence of TB.

Highlights

In countries with low incidence of TB, vulnerable populations, such as persons living in prisons [8] and shelters [9] and hard-to-reach populations [10,11,12,13], are at high risk for TB [3]
Study Population The immigrant population was recruited through a screening program designed to complement the National Health Service routine program to detect latent TB infection (LTBI) and TB in the general population, i.e., passive case finding and contact tracing of patients with active TB
From 1991 through 2010, a total of 27,358 socially marginalized immigrants who attended the screening program in Turin were considered at risk for active pulmonary TB

Summary

Introduction

In countries with low incidence of TB, vulnerable populations, such as persons living in prisons [8] and shelters [9] and hard-to-reach populations [10,11,12,13], are at high risk for TB [3]. Marginalized immigrants have the combined risk of coming from countries with high incidence of TB and being vulnerable because of their relegated social position in countries of destination [14]. No data have been published on incidence of infection, the key indicator of Mycobacterium tuberculosis transmission, among socially marginalized immigrants. Knowledge of these parameters among socially marginalized groups could inform control strategies for TB in countries in which TB incidence is low. We estimated the prevalence of and risk factors for active TB and LTBI, as well as the incidence of infection, among socially marginalized immigrants in an area of western Europe where incidence of TB is low. The estimated TB incidence during the study period, 1991–2010, was relatively stable (≈20 cases/100,000 persons), and in 2010, an increasing proportion of cases (»70%) occurred among foreign-born persons [18,19,20]

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