Series 2:Invisible Threats: A Global Scoping Review of Risk Factors for Tuberculosis Infection

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Résumé

Background: Tuberculosis (TB) remains a major global health challenge, with Mycobacterium
tuberculosis (M. tuberculosis) causing significant morbidity and mortality mainly in highburden
countries. Following exposure to M. tuberculosis, individuals may become infected,
developing TB infection (TBI) through inhalation of the bacillus: this affects approximately
one-fourth of the global population and serves as a critical reservoir for potential disease
reactivation and transmission. The risk of being infected with M. tuberculosis is shaped
by bacterial load of people with TB, contact patterns, environmental factors, and host
susceptibility, particularly in high-risk congregate settings. Elucidating these determinants
is instrumental for optimising TB prevention and control strategies. Methods: A preliminary
PubMed search was conducted on 25 August 2024, using the keywords “latent tuberculosis
infection,” “risk factors,” and “systematic review.” Targeted reviews were then performed in
November 2024 to examine factors influencing progression from exposure to M. tuberculosis
to TBI. Systematic reviews published between January 2000 and November 2024 were
included. Results: The scoping review analysed eight systematic reviews, grouping findings
into three key themes: (1) proximity and behavioural risk factors; (2) environmental risk
factors; and (3) host immune vulnerabilities. Close contact with people with TB in crowded
settings, such as dormitories, healthcare facilities, and prisons, was strongly associated
with an elevated risk of TBI. Healthcare workers travelling from low- to high-incidence
regions faced the highest risk due to frequent exposure to M. tuberculosis, while military
personnel and general travellers had lower risks. Environmental exposures, including
second-hand smoke and inadequate ventilation, further heightened susceptibility among
children and adults. Host immune risk factors, such as advanced age, low body mass indexlack of BCG vaccination, and metabolic disorders such as diabetes, markedly increase
susceptibility to TBI. The interplay between proximity, behavioural and environmental risk
factors, and host immune vulnerabilities highlights the multifactorial nature of TBI risk.
Conclusion: Effective TBI control demands a multifaceted approach, combining robust
infection prevention and control measures, comorbidity management, and mitigation of
behavioural risk factors like smoking. Tailored strategies are crucial for high-risk settings
such as healthcare facilities and prisons. Multisectoral collaboration is essential to address
key risk factors and protect vulnerable populations from progressing to TBI.

Mots-clés

Mycobacterium tuberculosis; tuberculosis infection; latent tuberculosis infection; proximity and behavioural risk factors; environmental risk factors; host immune vulnerabilities