BackgroundTuberculosis is endemic in Cape Town, South Africa where a majority of the population become tuberculosis infected before adulthood. While social contact patterns impacting tuberculosis and other respiratory disease spread have been studied, the environmental determinants driving airborne transmission have not been quantified.MethodsIndoor carbon dioxide levels above outdoor levels reflect the balance of exhaled breath by room occupants and ventilation. We developed a portable monitor to continuously sample carbon dioxide levels, which were combined with social contact diary records to estimate daily rebreathed litres. A pilot study established the practicality of monitor use up to 48-hours. We then estimated the daily volumes of air rebreathed by adolescents living in a crowded township.ResultsOne hundred eight daily records were obtained from 63 adolescents aged between 12- and 20-years. Forty-five lived in wooden shacks and 18 in brick-built homes with a median household of 4 members (range 2–9). Mean daily volume of rebreathed air was 120.6 (standard error: 8.0) litres/day, with location contributions from household (48%), school (44%), visited households (4%), transport (0.5%) and other locations (3.4%). Independent predictors of daily rebreathed volumes included household type (p = 0.002), number of household occupants (p = 0.021), number of sleeping space occupants (p = 0.022) and winter season (p<0.001).ConclusionsWe demonstrated the practical measurement of carbon dioxide levels to which individuals are exposed in a sequence of non-steady state indoor environments. A novel metric of rebreathed air volume reflects social and environmental factors associated with airborne infection and can identify locations with high transmission potential.

Background: In the beginning of the COVID-19 pandemic, cloth face coverings developed into an essential and widely mandated non-pharmaceutical intervention to mitigate the impact of COVID-19. With the introduction of face mask orders to prevent the spread of COVID-19, the general public may have turned to their state government or health department's website to find information related to face coverings.Aims: This study seeks to evaluate the readability, suitability, and content of initial masking guidance on state government or state health department websites from U.S. states with face mask orders during the beginning of the COVID-19 pandemic.Methods: From states with mask mandates (n=41), masking guidance and education related to face coverings was collected from June 1st, 2020 to July 15th, 2020 from state government and state health department websites. Each state's education on face coverings was assessed using three readability indices: Fog Index (FOG), the Simplified Measure of Gobbledygook (SMOG), and the Flesch Kincaid Grade level and the Suitability Assessment for Materials tool for suitability.A novel masking guidance-specific score was developed to evaluate the content on face coverings.Results: Masking guidance varied in literacy demand, format, and content. The mean readability of 11.54 (SD=1.85) surpasses the recommended 6-7 th grade level. The mean SAM score of 55.9 (SD=9.6) is considered "adequate" for suitability. The mean content score was 5.85 v (SD=1.30), and only 18 states' masking guidance contained all seven points of information related to face coverings.Conclusions: Although most states' initial masking guidance was suitable and contained necessary information, the inconsistency and high readability prevented the American public from educating themselves, ultimately limiting adherence to the mask mandates. During a public health crisis like the COVID-19 pandemic, readable, suitable, and comprehensive and consistent online information is vital in encouraging adherence to public health orders and promoting other preventive health behaviors. vi Table of ContentsPreface .