Published: 9 November 2021
Authors: Erick W. Bunyasi, Keren Middelkoop, Anastasia Koch, Zeenat Hoosen, Humphrey Mulenga, Angelique K. K. Luabeya, Justin Shenje, Simon C. Mendelsohn, Michele Tameris, Thomas J. Scriba, Digby F. Warner, Robin Wood, Jason R. Andrews, and Mark Hatherill
Source: This abstract has been sourced from NZ Respiratory Research Review Issue 199
Rationale: South African adolescents carry a high tuberculosis disease burden. It is not known if schools are high-risk settings for Mycobacterium tuberculosis (MTB) transmission.
Objectives: To detect airborne MTB genomic DNA in classrooms.
Methods: We studied 72 classrooms occupied by 2,262 students in two South African schools. High-volume air filtration was performed for median 40 (interquartile range [IQR], 35–54) minutes and assayed by droplet digital PCR (ddPCR)-targeting MTB region of difference 9 (RD9), with concurrent CO2 concentration measurement. Classroom data were benchmarked against public health clinics. Students who consented to individual tuberculosis screening completed a questionnaire and sputum collection (Xpert MTB/RIF Ultra) if symptom positive. Poisson statistics were used for MTB RD9 copy quantification.
Measurements and Main Results: ddPCR assays were positive in 13/72 (18.1%) classrooms and 4/39 (10.3%) clinic measurements (P = 0.276). Median ambient CO2 concentration was 886 (IQR, 747–1223) ppm in classrooms versus 490 (IQR, 405–587) ppm in clinics (P < 0.001). Average airborne concentration of MTB RD9 was 3.61 copies per 180,000 liters in classrooms versus 1.74 copies per 180,000 liters in clinics (P = 0.280). Across all classrooms, the average risk of an occupant inhaling one MTB RD9 copy was estimated as 0.71% during one standard lesson of 35 minutes. Among 1,836/2,262 (81.2%) students who consented to screening, 21/90 (23.3%) symptomatic students produced a sputum sample, of which one was Xpert MTB/RIF Ultra positive.
Conclusions: Airborne MTB genomic DNA was detected frequently in high school classrooms. Instantaneous risk of classroom exposure was similar to the risk in public health clinics.
Link to abstract
NZ Respiratory Research Review Issue 199