Who
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Participants:
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Index patients: 2,771 individuals aged 15–60 years with microbiologically confirmed pulmonary TB.
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Household contacts (HHCs): 10,745 contacts aged 0–60 years (participants >60 excluded).
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Key subgroups:
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Index patients categorized as Youth (15–24 years) or Adults (25–60 years).
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HHCs categorized as Children (0–14 years), Youth (15–24 years), and Adults (25–60 years).
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What
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Main findings:
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Child household contacts exposed to youth index patients had a lower prevalence of TB infection at enrollment compared with those exposed to adult index patients (adjusted PRR = 0.77; 95% CI: 0.67–0.87).
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Index patient age was not associated with the incidence of TB infection among household contacts over 12 months.
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Children and youth contacts had significantly lower incidence of TB infection than adult contacts, regardless of index patient age.
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Whole-genome sequencing (WGS) showed a lower proportion of genetically linked transmission pairs for youth index patients compared with adults, though this difference was not statistically significant.
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Interpretation:
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Youths appear to contribute less to within-household TB transmission than adults, suggesting that their transmission risk may occur more often outside the household.
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When
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Study period: September 2009 to August 2012.
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Follow-up duration: 12 months after household enrollment.
Where
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Setting: Lima, Peru.
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Healthcare context: 106 public health centers serving approximately 3 million people.
Why
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To determine whether the age of TB index patients, particularly youth (15–24 years), influences the risk of TB transmission to household contacts, with a focus on children as a marker of recent transmission.
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To address gaps in understanding age-specific transmission dynamics and inform targeted TB control strategies.
How
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Study design: Prospective household cohort study.
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TB infection assessment:
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Baseline tuberculin skin test (TST) to measure prevalence.
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Repeat TSTs at 6 and 12 months to measure incidence.
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TB disease classification:
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Co-prevalent TB (≤14 days after enrollment) vs secondary TB (>14 days).
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Transmission confirmation:
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Whole-genome sequencing of Mycobacterium tuberculosis isolates to assess genetic linkage between index and secondary cases.
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Analysis:
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Multivariable regression and survival analyses adjusting for demographic, behavioral, socioeconomic, and nutritional factors.