Disease Transmission by Patients With Subclinical Tuberculosis

Abstract

Background Subclinical tuberculosis has been increasingly recognized as a separate state in the spectrum of the disease. However, evidence on the transmissibility of subclinical tuberculosis is still inconclusive. Methods We reanalysed the data from the 2007 combined tuberculosis prevalence and tuberculin surveys in Vietnam. Poisson regression with robust standard errors was conducted to assess the effect of clinical presentation of tuberculosis patients in the household on tuberculin skin test (TST) positivity among children aged 6-14 years who participated in the tuberculin survey, adjusting for child's age, smear status of the index patient, and other covariates. Results In the multivariate analysis, we found significantly increased risks for TST positivity in children living with clinical, smear-positive tuberculosis patients, compared with those living without tuberculosis patients (adjusted risk ratio 3.04, 95%CI 2.00-4.63) and with those living with subclinical tuberculosis patients adjusting for index smear status (aRR 2.26, 95%CI 1.03-4.96). Among children aged 6-10 years, those living with clinical, smear-positive tuberculosis patients, and those living with subclinical, smear-positive tuberculosis patients, had similarly increased risks of TST positivity compared with those living without tuberculosis patients, with aRRs of 3.56 (95%CI 1.91-6.62) and 3.11 (95%CI 1.44-6.72), respectively. Conclusion Our findings support the hypothesis that smear-positive subclinical tuberculosis contributes to Mycobacterium tuberculosis transmission. To eliminate tuberculosis in 2035, control strategies need to address subclinical presentations of the disease.

PersistentMycobacterium tuberculosisbioaerosol release in a tuberculosis-endemic setting

“…Through this lens, data from extensive community TB screening efforts utilizing sputum-GeneXpert – which have identified large numbers of asymptomatic cases (Moyo et al, 2022) – support the notion of unrecognized transmitters in high-burden communities. And, while these results accommodate the potential for Mtb transmission to occur prior to the development of recognizable TB symptoms (Nguyen et al, 2023), they nevertheless rely on sputum production (itself a symptom of disease) for the detection of Mtb . This dependency on sputum production imposes a significant constraint on attempts to detect individuals with early TB, and is exacerbated by the difficulties encountered in obtaining useable samples from many individuals (Pai et al, 2023).…”

Estimating the contribution of subclinical tuberculosis disease to transmission: An individual patient data analysis from prevalence surveys

“…There are no other estimates for the infectiousness of subclinical TB relative to clinical TB in the literature with which to compare our results. Using data from the 2007 Viet Nam prevalence survey, however, Nguyen et al, 2023 find that among children aged 6–10 years, those living with clinical, smear-positive TB, and those living with subclinical, smear-positive TB had similarly increased risks of TST positivity compared with those living without TB. Moreover, a recent small study from Uganda found no evidence of a difference in cumulative infection rates in household contacts of patients who did or did not report symptoms ( Baik et al, 2021 ).…”

Subclinical tuberculosis: a meta-analysis of prevalence and scoping review of definitions, prevalence and clinical characteristics

“…This is expected since the latter group would likely be presenting at the later stages of the disease [ 1 ]. Data from prevalence and tuberculin surveys in Vietnam and mathematical models have further underscored the potential contribution of people with bacteriologically confirmed subclinical TB to M. tuberculosis transmission [ 9 , 83 , 84 ]. Considering the potential infectiousness of this population, relying on passive case finding [ 7 , 84 ] upon presentation at the health facilities or symptoms-based screening approaches could lead to further diagnostic delays, poorer prognosis and more severe post-TB sequelae.…”

“…Data from representative TB prevalence surveys suggest that 50.4% of the prevalent bacteriologically confirmed TB in the general community was subclinical [ 5 ]. While only around half of the people with subclinical TB will progress to clinical TB [ 6 ], their potential ability to transmit the disease has serious implications for public health and the global efforts to end TB by 2035 [ 7 – 9 ]. Pathological changes occur while affected individuals remain at the subclinical stage [ 1 ], making it critical to identify and treat those at this disease phase.…”