Transmission of Mycobacterium Tuberculosis in Households and the Community: A Systematic Review and Meta-Analysis

Abstract

The individual- and population-level impact of household tuberculosis exposure on transmission is unclear but may have implications for the effectiveness and implementation of control interventions. We systematically searched for and included studies in which latent tuberculosis infection was assessed in 2 groups: children exposed and unexposed to a household member with tuberculosis. We also extracted data on the smear and culture status of index cases, the age and bacillus Calmette-Guérin vaccination status of contacts, and study design characteristics. Of 6,176 citations identified from our search strategy, 26 studies (13,999 children with household exposure to tuberculosis and 174,097 children without) from 1929-2015 met inclusion criteria. Exposed children were 3.79 (95% confidence interval (CI): 3.01, 4.78) times more likely to be infected than were their community counterparts. Metaregression demonstrated higher infection among children aged 0-4 years of age compared with children aged 10-14 years (ratio of odds ratios = 2.24, 95% CI: 1.43, 3.51) and among smear-positive versus smear-negative index cases (ratio of odds ratios = 5.45, 95% CI: 3.43, 8.64). At the population level, we estimated that a small proportion (<20%) of transmission was attributable to household exposure. Our results suggest that targeting tuberculosis prevention efforts to household contacts is highly effective. However, a large proportion of transmission at the population level may occur outside the household.

Keywords: Mycobacterium tuberculosis; contact tracing; recent transmission; systematic review; tuberculosis.

Figure 1.

Flow diagram for search and selection of 26 included studies, for a meta-analysis of the assessment of latent tuberculosis infection among children who were exposed to tuberculosis in the household and children who were not, published during 1929–2015.

Figure 2.

Forest plot of latent tuberculosis infection for children who were exposed to tuberculosis in the household and children who were not, from a meta-analysis of 26 studies published during 1929–2015. Squares with bars represent study-specific odds ratios (ORs) with confidence intervals (CIs), and the diamond represents the summary odds ratio estimate. A random-effects model with DerSimonian and Laird weights, equalizing the weight of the studies to the pooled estimate, was used to derive the summary estimate. Assessment of heterogeneity: I² = 93.6%; P = 0.000.

Figure 3.

Forest plot of latent tuberculosis infection in household-contact and community-control groups by the smear and culture status of the index case from a meta-analysis of 26 studies published during 1929–2015. Squares with bars represent study-specific odds ratios (ORs) with confidence intervals (CIs), and each diamond represents the summary OR estimate for the stratum above it. A random-effects model with DerSimonian and Laird weights, equalizing the weight of the studies to the pooled estimate, was used to derive each stratified summary estimate. Assessments of heterogeneity: sputum smear–negative, culture-negative index cases, I² = 72.9% (P = 0.005); sputum smear–negative, culture-positive index cases, I² = 87.7% (P = 0.000); sputum smear–positive, culture-positive index cases, I² = 90.6% (P = 0.000).