# Series 1: Behind the Spread: A Scoping Review of Risk Factors for Exposure to Mycobacterium tuberculosis

## TL;DR

This review identifies social and environmental factors like homelessness and air pollution that increase the risk of tuberculosis transmission.

## Contribution

The study provides a comprehensive synthesis of recent systematic reviews on emerging and established risk factors for TB exposure.

## Key findings

- Key risk factors include homelessness, migration, urbanization, and air pollution.
- Social and environmental determinants are interrelated and drive TB transmission.
- Poverty-related factors like overcrowding and limited healthcare access worsen TB risks.

## Abstract

Background: Tuberculosis (TB) remains a major global health challenge, with transmission influenced by the incidence of contagious people with TB, the duration of infectivity, and the probability of contact with susceptible individuals. This review synthesizes recent evidence on established and emerging risk factors influencing TB transmission, particularly in light of global trends such as migration, urbanization, and demographic shifts, to guide future prevention and control strategies. This scoping review maps and synthesizes evidence from systematic reviews on risk factors for Mycobacterium tuberculosis exposure. Methods: A preliminary general literature search was conducted in PubMed on 25 August 2024, using the keywords “tuberculosis,” “risk factors,” and “systematic review.” A subsequent targeted search focused on systematic reviews published since 2000 that examined social and environmental determinants of exposure to M. tuberculosis identified in the general search. Original research and reviews spanning pre-2000 were excluded. Data extraction and synthesis followed PRISMA-ScR guidelines. Results: Of the 344 systematic reviews identified, 14 met the eligibility criteria, reporting on key risk factors contributing to the incidence of contagious people with TB, the duration of infectivity, and the probability of contact. These risk factors included homelessness, migration, occupational exposure, urbanization, climate change, and air pollution. The findings emphasize the complex interrelated role of social and environmental determinants in driving TB transmission. Conclusion: This review highlights the need for a multi-sectoral approach to TB, as climate change, air pollution, overcrowding, stigma, and limited healthcare access exacerbate established risks related to poverty. Effective prevention and control require targeted interventions that address these interconnected factors.