**1. Introduction**

Tuberculosis (TB) is the main cause of death from infectious disease globally. Drug-resistant forms of the disease are a major risk to global health security [1]. The WHO estimates that 10.4 million individuals became ill with TB and 1.7 million died in 2016. Despite a fall in mortality rate by 3% per year, TB remains the ninth leading cause of death worldwide, resulting in 1.3 million deaths in HIV-negative people and almost 400,000 deaths in HIV-positive people [2,3]. TB epidemiology in most low-incidence countries is characterized by a low rate of transmission in the general population, occasional outbreaks and a majority of TB cases generated from progression of latent tuberculosis infection (LTBI) rather than local transmission [4]. Migration flows have changed drastically since the beginning of the 21st century. Because most immigrants come from countries with a high incidence

of tuberculosis, the contribution of the migrant population to new cases of tuberculosis is stronger in relative terms than for its weight in the total population [5]. For this reason, it is necessary to both diagnose TB early by including universal drug susceptibility testing, and to implement systematic screening for TB in selected high-risk groups. Early detection helps to reduce the risk of further TB transmission, poor treatment outcomes and undesirable health sequelae, thus also decreasing adverse social and economic consequences of the disease [6,7].

In the last 50 years, the annual incidence of TB in Italy decreased by about 70%, from around 25 to 7 cases per 100,000 individuals, and it now seems to be quite stable [8]. In this country, however, only limited data are available about TB epidemiology in potentially high-risk groups such as undocumented immigrants. Consequently, TB prevalence and risk factors in illegal immigrants are unknown. Furthermore, they have not been monitored over time. In spite of this, while national guidelines [9] recommend LTBI screening in high-risk subjects such as pulmonary TB contacts, HIV-infected patients, and patients undergoing immunosuppressive therapy and health care workers, less attention is devoted to the immigrant population, whereby early detection of active and LTBI cases should be pursued using the following strategies [10]: screening for both active TB and LTBI and therapy of LTBI in children, chest X-ray (CXR) screening for active TB in symptomatic subjects especially recent irregular immigrants. In addition, screening for active and latent TB in asymptomatic adults with recent immigration (<5 years) or living in social and health conditions of marginalization has no strong evidence. This also applies to undocumented immigrants, although these may represent an important source of LTBI and active TB. At the Centre for Health of Foreign Family (CFF), systematic screening for both active TB and LTBI had been performed since January 2012.
