Risk Factors for TB Infection: Scoping Review Highlights Congregate Settings and Host Vulnerabilities

A global scoping review synthesizing systematic-review evidence on determinants of tuberculosis infection (TBI) describes a multi-domain set of tuberculosis infection (TBI) risk factors, spanning proximity and behavioural exposures, environmental conditions, and host immune vulnerabilities. Across the synthesis, the authors return to congregate and crowded contexts as settings where exposure intensity may be amplified, explicitly including prisons among the environments discussed. Their organizing frame links where exposure occurs with who may be more susceptible once exposed.

The authors report synthesizing eight systematic reviews published between January 2000 and November 2024. They identified relevant reviews through a PubMed search and then conducted targeted reviews to examine factors influencing progression from exposure to M. tuberculosis to TBI. Reported determinants are grouped into three themes: (1) proximity and behavioural risk factors, (2) environmental risk factors, and (3) host immune vulnerabilities. Within this structure, determinants are described as interacting rather than operating in isolation, with the themes used as an organizing approach for heterogeneous evidence.

For proximity and behavioural factors, the review emphasizes repeated or prolonged close contact with people with TB as a recurring context in which higher TBI risk is reported, particularly when contact patterns concentrate exposure. Occupational exposure is summarized as a prominent example: healthcare workers are described as having elevated risk in association with frequent exposure during clinical work and training, and travel from low- to high-incidence regions is discussed as another circumstance in which occupational proximity may shape risk. The synthesis also highlights incarceration as a setting-related exposure pattern, describing correctional environments as contexts where the duration and repetition of close contact are considered relevant. In describing “highest-risk” contexts, the review repeatedly cites crowded congregate environments—dormitories, healthcare facilities, and prisons—as examples where close-contact exposure can be intensified; prisons are portrayed as one repeatedly cited amplification context for TBI risk.

Environmental modifiers are grouped around conditions that may increase exposure opportunity or susceptibility, including inadequate ventilation as well as exposures such as second-hand smoke and indoor air pollution. Separately, the authors summarize host immune vulnerabilities reported alongside these environmental considerations, including age, low body mass index, lack of BCG vaccination, and metabolic disorders such as diabetes. Across these categories, the review frames risk as shaped by both indoor environment characteristics and individual susceptibility factors that may influence whether exposure progresses to measurable infection. Taken together, the synthesis presents TBI risk as a multi-domain construct spanning environment and host factors in addition to exposure patterns.

In their conclusions, the authors state that effective TB infection control demands a multifaceted approach combining infection prevention and control measures, comorbidity management, and mitigation of behavioral risk factors such as smoking. They also emphasize that strategies should be tailored to high-risk settings, explicitly naming healthcare facilities and prisons as examples where such tailoring is crucial. The authors further describe multisectoral collaboration as important for addressing the drivers they summarize across exposure, environment, and host vulnerability domains. As presented in the review, tailoring across high-risk contexts is central to the multifaceted framing of TBI control.

Key Takeaways:

• The scoping review synthesizes eight systematic reviews (2000–2024) and organizes reported determinants of TBI into three themes: proximity/behavioural, environmental, and host immune vulnerabilities.
• Close or prolonged contact in crowded congregate settings—including healthcare facilities and prisons—appears repeatedly in the synthesis as a context associated with higher reported TBI risk.
• The authors conclude that TB infection control in high-risk settings benefits from tailored strategies that combine infection prevention and control measures with attention to comorbidities and behavioural risk factors.