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First 5000 Characters:Background 28 Healthcare facilities are important sites for the transmission of pathogens spread via bioaerosols, 29 such as Mycobacterium tuberculosis (Mtb). Natural ventilation can play an important role in reducing 30 this transmission. In primary health care (PHC) clinics in low and middle-income settings, susceptible 31 people, including healthcare workers, are exposed to individuals with infectious pulmonary 32 tuberculosis. We measured rates of natural ventilation in PHC clinics in KwaZulu-Natal and Western 33
Cape provinces, South Africa. 34
Methods and Findings
We measured ventilation in clinic spaces using a tracer-gas release method. In spaces where this was 36 not possible, we estimated ventilation using data on indoor and outdoor carbon dioxide levels, 37 under reasonable assumptions about occupants' metabolic rates. Ventilation was measured i) under 38 usual conditions and ii) with all windows and doors fully open. We used these ventilation rates to 39 estimate the risk of Mtb transmission using the Wells-Riley Equation. We obtained ventilation 40 measurements in 33 clinical spaces in 10 clinics: 13 consultation rooms, 16 waiting areas and 4 other 41 clinical spaces. Under usual conditions, the absolute ventilation rate was much higher in waiting 42 rooms (median 1769 m 3 /hr, range 338-4815 m 3 /hr) than in consultation rooms (median 197 m 3 /hr, 43 range 0-1451 m 3 /hr). Ventilation was better in permanent than in temporary structures. When 44 compared with usual conditions, fully opening existing doors and windows resulted in a median two-45 fold increase in ventilation. Our Wells-Riley estimates show that, following sustained exposure, or 46 contact with highly infectious index cases, some risk of Mtb infection may persist in the best 47 ventilated clinical spaces unless other components of transmission risk are also addressed. 48 Conclusions 49 Among the clinical spaces studied, we observed substantial variation in natural ventilation. 50 Ventilation interventions may have considerable impact on Mtb transmission in this setting. We 51 recommend these form part of a package of infection prevention and control interventions. 52 53 54 . CC-BY 4.0 International license It is made available under a perpetuity.
is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) : medRxiv preprint 55 Good ventilation in congregate spaces can reduce transmission of airborne pathogens, such as 56 Mycobacterium tuberculosis (Mtb) , Rubeola virus (measles), and SARS-CoV-2 . However, 57 ventilation rates are difficult to measure and there are limited data available on ventilation rates in 58 public spaces, such as clinics, in sub-Saharan Africa . 59 Healthcare facilities bring together infectious and susceptible individuals and are important sites for 60 the transmission of airborne pathogens. This is particularly true for Mtb . Clinic attendees 61 including vulnerable populations, such as people living with HIV, may inhale bioaerosols containing 62 Mtb produced by individuals with pulmonary tuberculosis (TB) attending the same facility 63 . Mtb is an important occupational health concern, with health workers at 64 greater risk than the general population of infection and reinfection and, as a result, developing 65 active TB disease . 66 Improved ventilation, an infection prevention and control (IPC) intervention, decreases the risk of 67 infection by removing droplet nuclei containing aerosolised Mtb. Natural ventilation plays a key role 68 in low and middle-income settings where the resources and infrastructure needed for mechanical 69 ventilation systems are usually unavailable . Natural ventilation can have comparable or superior 70 performance to mechanical ventilation systems . However, rates will vary with changes in wind 71 speed or direction, and inadequate rates of natural ventilation may occur in poorly designed 72 buildings . 73 We aimed to describe the ventilation of waiting areas, consultation rooms, and other clinical spaces 74 across ten primary healthcare clinics (PHCs) in South Africa. Our ventilation experiments were 75 undertaken as part of an interdisciplinary project called Umoya omuhle (meaning "good air" in Zulu), 76 which used a whole systems approach to understand Mtb transmission and TB IPC in PHC clinics in 77 South Africa . 78 Methods 79 Setting 80 Ventilation experiments were performed in five PHC clinics in KwaZulu-Natal and five in Western 81 Cape province, South Africa, between December 2018 and December 2019. These facilities were 82 built between the 1980s and early 2010s and serve both urban and rural populations. They were 83
selected to be broadly representative of PHC clinics in the two provinces with respect to location, 84 age of building, and type of clinic. Each clinic had a unique design, though some clinics had several 85 r