Modelling the effect of infection prevention and control measures on rate ofMycobacterium tuberculosistransmission to clinic attendees in primary health clinics in South Africa

Abstract

BackgroundElevated rates of tuberculosis in healthcare workers demonstrate the high rate of Mycobacterium tuberculosis (Mtb) transmission in health facilities in high-burden settings. In the context of a project taking a whole systems approach to tuberculosis infection prevention and control (IPC), we aimed to evaluate the potential impact of conventional and novel IPC measures on Mtb transmission to patients and other clinic attendees.MethodsAn individual-based model of patient movements through clinics, ventilation in waiting areas, and Mtb transmission was developed, and parameterised using empirical data from eight clinics in two provinces in South Africa. Seven interventions—codeveloped with health professionals and policy-makers—were simulated: (1) queue management systems with outdoor waiting areas, (2) ultraviolet germicidal irradiation (UVGI) systems, (3) appointment systems, (4) opening windows and doors, (5) surgical mask wearing by clinic attendees, (6) simple clinic retrofits and (7) increased coverage of long antiretroviral therapy prescriptions and community medicine collection points through the Central Chronic Medicine Dispensing and Distribution (CCMDD) service.ResultsIn the model, (1) outdoor waiting areas reduced the transmission to clinic attendees by 83% (IQR 76%–88%), (2) UVGI by 77% (IQR 64%–85%), (3) appointment systems by 62% (IQR 45%–75%), (4) opening windows and doors by 55% (IQR 25%–72%), (5) masks by 47% (IQR 42%–50%), (6) clinic retrofits by 45% (IQR 16%–64%) and (7) increasing the coverage of CCMDD by 22% (IQR 12%–32%).ConclusionsThe majority of the interventions achieved median reductions in the rate of transmission to clinic attendees of at least 45%, meaning that a range of highly effective intervention options are available, that can be tailored to the local context. Measures that are not traditionally considered to be IPC interventions, such as appointment systems, may be as effective as more traditional IPC measures, such as mask wearing.

Direct estimates of absolute ventilation in primary health care clinics in South Africa

“…As part of the wider Umoya omuhle project, we have modelled the impact of IPC interventions implemented in clinics, including improvements in natural ventilation, on transmission both within clinics [39] and in surrounding communities [40]. Cost effectiveness analyses of these interventions CO2 release experiments are a robust approach to measuring ventilation.…”

Estimating the contribution of transmission in primary healthcare clinics to community-wide TB disease incidence, and the impact of infection prevention and control interventions, in KwaZulu-Natal, South Africa

“…Seven potential IPC interventions had been identified in qualitative research and system dynamics modelling exercises conducted as part of the Umoya omuhle project 5. The effect of the interventions on patient contacts and infection risk in eight clinics were estimated in previous modelling work, using a within-clinics model that simulated the flow of patients through clinics, and ventilation rates and infection risk in clinic waiting areas 6. Results were aggregated across all clinics, giving a single estimate for the effect of each intervention.…”

“…5 The effect of the interventions on patient contacts and infection risk in eight clinics were estimated in previous modelling work, using a within-clinics model that simulated the flow of patients through clinics, and ventilation rates and infection risk in clinic waiting areas. 6 Results were aggregated across all clinics, giving a single estimate for the effect of each intervention. The interventions were:…”

“…As part of the project, system dynamics modelling was used to identify potential IPC interventions that local policy makers and health professionals active at clinic and province levels ranked highly in terms of both feasibility of implementation and perceived likely impact on overall and multidrug resistant (MDR) Mycobacterium tuberculosis ( Mtb ) transmission in clinics 5. The impact of the interventions on the rate of Mtb transmission to clinic attendees was then estimated using an IBM that simulated the flow of patients through clinics, and ventilation rates and infection risk in clinic waiting areas 6…”

“…5 The impact of the interventions on the rate of Mtb transmission to clinic attendees was then estimated using an IBM that simulated the flow of patients through clinics, and ventilation rates and infection risk in clinic waiting areas. 6 …”