Tuberculosis is shifting to cities: study

Tuberculosis remains a leading infectious killer worldwide, but the size and shape of the epidemic can look very different in cities compared with rural areas. Urban and rural settings vary in transmission dynamics, social and structural drivers, and access to health care, and those differences affect how many people have active pulmonary TB and whether they are found and treated. To clarify these patterns, a team led by corresponding author Peter MacPherson carried out a systematic review and meta-analysis focused on adult pulmonary TB prevalence in low- and middle-income countries. The researchers looked for community-representative prevalence surveys conducted from 1 January 1993 to 14 October 2025, and intentionally excluded studies that only sampled people with symptoms or people already seeking care, as well as surveys carried out in congregate settings such as prisons, universities, or health facilities. Their goal was to compare directly measured TB prevalence in urban versus rural populations, to see how the balance has changed over time and across regions, and to produce estimates that could guide public health planning.

The review searched multiple databases including PubMed, Embase, Global Health, the Cochrane Library, Africa Index Medicus, LILACS, and SciELO and assessed the risk of bias for each prevalence survey. In total the analysis included 47 surveys conducted between 2000 and 2024, covering 2,454,443 participants. The team used Bayesian multilevel meta-regression to pool urban-to-rural prevalence ratios (PRs) for bacteriologically-confirmed and smear-positive TB overall and by World Health Organization (WHO) region, and examined trends over time and relationships with survey features such as screening algorithm, national TB incidence, percentage urban, and representativeness. They also fitted a Bayesian multivariate model to WHO incidence and case detection ratio data and combined that with assumptions about the duration of treated and untreated TB and the distribution of urban and rural populations to estimate numbers of people with prevalent TB from 2000 to 2024. Pooled results showed an urban-to-rural PR of 1.09 (95% credible interval [CrI]: 0.90, 1.30) for bacteriologically-confirmed TB and 1.24 (95% CrI: 0.94, 1.61) for smear-positive TB. Regionally, the African Region averaged higher urban prevalence (PR 1.18, 95% CrI: 0.91, 1.52), while the Western Pacific and South-East Asia Regions had broadly similar urban and rural prevalence. Time trends suggested a mean annual increase of 2.4% (95% CrI: -0.8%, 6.0%) in the urban-to-rural bacteriologically-confirmed PR. For 2024 in the 26 study countries combined, the researchers estimated about 6.6 million prevalent TB cases (49%) in urban areas and 6.8 million (51%) in rural areas, noting wide credible intervals and important data gaps.

The analysis indicates that, over the past two decades, TB epidemics in the studied countries have become more urbanised in both relative and absolute terms, though the timing and extent of that shift vary widely between countries and regions. Within nearly all countries represented in the review, the share of TB cases occurring in urban areas increased between 2000 and 2024. This pattern matters because crowded living conditions, crowding in public transport, informal settlements, and differences in access to diagnosis and treatment can change how TB spreads and who is most affected. The study highlights the need for public health responses that are tailored to local urban and rural realities: interventions that work in dense city environments — strengthened active case finding, tailored outreach, and improved diagnostic access in informal settlements — may differ from those needed where people live far from clinics. The authors also point to important limitations, such as inconsistent definitions of 'urban' and 'rural' and missing data from some world regions (for example, parts of the Americas and Europe), underscoring the need for standardized, nationally representative prevalence surveys and better surveillance to guide resource allocation and program design aimed at ending TB.