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Natural ventilation reduces high TB transmission risk in traditional homes in rural KwaZulu-Natal, South Africa.

Lygizos M, Shenoi SV, Brooks RP, Bhushan A, Brust JC, Zelterman D, Deng Y, Northrup V, Moll AP, Friedland GH - BMC Infect. Dis. (2013)

Bottom Line: Two hundred eighteen ventilation measurements were taken in 24 traditional homes.Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio.Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold.

View Article: PubMed Central - HTML - PubMed

Affiliation: Yale University School of Medicine, AIDS Program, New Haven, CT, USA.

ABSTRACT

Background: Transmission of drug susceptible and drug resistant TB occurs in health care facilities, and community and households settings, particularly in highly prevalent TB and HIV areas. There is a paucity of data regarding factors that may affect TB transmission risk in household settings. We evaluated air exchange and the impact of natural ventilation on estimated TB transmission risk in traditional Zulu homes in rural South Africa.

Methods: We utilized a carbon dioxide decay technique to measure ventilation in air changes per hour (ACH). We evaluated predominant home types to determine factors affecting ACH and used the Wells-Riley equation to estimate TB transmission risk.

Results: Two hundred eighteen ventilation measurements were taken in 24 traditional homes. All had low ventilation at baseline when windows were closed (mean ACH = 3, SD = 3.0), with estimated TB transmission risk of 55.4% over a ten hour period of exposure to an infectious TB patient. There was significant improvement with opening windows and door, reaching a mean ACH of 20 (SD = 13.1, p < 0.0001) resulting in significant decrease in estimated TB transmission risk to 9.6% (p < 0.0001). Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio. Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold.

Conclusions: There is high estimated risk of TB transmission in traditional homes of infectious TB patients in rural South Africa. Improving natural ventilation may decrease household TB transmission risk and, combined with other strategies, may enhance TB control efforts.

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Estimated Risk of TB Infection by Exposure Time. Risk of TB infection after various durations of exposure to an active TB case under different ventilation conditions, as estimated using the Wells-Riley equation. Diamond: windows and door closed; Triangle: windows open; Circle: windows and door open together.
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Figure 3: Estimated Risk of TB Infection by Exposure Time. Risk of TB infection after various durations of exposure to an active TB case under different ventilation conditions, as estimated using the Wells-Riley equation. Diamond: windows and door closed; Triangle: windows open; Circle: windows and door open together.

Mentions: The estimated risk of TB transmission after ten hours of exposure to an infectious TB patient with windows and door closed was 55.4% (SD = 27.8%). This risk dropped significantly upon opening windows (21.5%, SD = 14.1%, p < 0.001), and further upon opening windows and door together (9.6%, SD = 4.7, p < 0.001) (Table 1, Figure 2b). The estimated risk of TB infection increased in parallel to exposure time (p < 0.001) (Figure 3). Despite the differences in ACH, there was no significant difference in estimated TB transmission risk under any condition between the two main home types (Table 1). Notably, the estimated risk with 2 hours of exposure in a closed room approximates that at 24 hours with windows and doors open (Figure 3).


Natural ventilation reduces high TB transmission risk in traditional homes in rural KwaZulu-Natal, South Africa.

Lygizos M, Shenoi SV, Brooks RP, Bhushan A, Brust JC, Zelterman D, Deng Y, Northrup V, Moll AP, Friedland GH - BMC Infect. Dis. (2013)

Estimated Risk of TB Infection by Exposure Time. Risk of TB infection after various durations of exposure to an active TB case under different ventilation conditions, as estimated using the Wells-Riley equation. Diamond: windows and door closed; Triangle: windows open; Circle: windows and door open together.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3716713&req=5

Figure 3: Estimated Risk of TB Infection by Exposure Time. Risk of TB infection after various durations of exposure to an active TB case under different ventilation conditions, as estimated using the Wells-Riley equation. Diamond: windows and door closed; Triangle: windows open; Circle: windows and door open together.
Mentions: The estimated risk of TB transmission after ten hours of exposure to an infectious TB patient with windows and door closed was 55.4% (SD = 27.8%). This risk dropped significantly upon opening windows (21.5%, SD = 14.1%, p < 0.001), and further upon opening windows and door together (9.6%, SD = 4.7, p < 0.001) (Table 1, Figure 2b). The estimated risk of TB infection increased in parallel to exposure time (p < 0.001) (Figure 3). Despite the differences in ACH, there was no significant difference in estimated TB transmission risk under any condition between the two main home types (Table 1). Notably, the estimated risk with 2 hours of exposure in a closed room approximates that at 24 hours with windows and doors open (Figure 3).

Bottom Line: Two hundred eighteen ventilation measurements were taken in 24 traditional homes.Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio.Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold.

View Article: PubMed Central - HTML - PubMed

Affiliation: Yale University School of Medicine, AIDS Program, New Haven, CT, USA.

ABSTRACT

Background: Transmission of drug susceptible and drug resistant TB occurs in health care facilities, and community and households settings, particularly in highly prevalent TB and HIV areas. There is a paucity of data regarding factors that may affect TB transmission risk in household settings. We evaluated air exchange and the impact of natural ventilation on estimated TB transmission risk in traditional Zulu homes in rural South Africa.

Methods: We utilized a carbon dioxide decay technique to measure ventilation in air changes per hour (ACH). We evaluated predominant home types to determine factors affecting ACH and used the Wells-Riley equation to estimate TB transmission risk.

Results: Two hundred eighteen ventilation measurements were taken in 24 traditional homes. All had low ventilation at baseline when windows were closed (mean ACH = 3, SD = 3.0), with estimated TB transmission risk of 55.4% over a ten hour period of exposure to an infectious TB patient. There was significant improvement with opening windows and door, reaching a mean ACH of 20 (SD = 13.1, p < 0.0001) resulting in significant decrease in estimated TB transmission risk to 9.6% (p < 0.0001). Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio. Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold.

Conclusions: There is high estimated risk of TB transmission in traditional homes of infectious TB patients in rural South Africa. Improving natural ventilation may decrease household TB transmission risk and, combined with other strategies, may enhance TB control efforts.

Show MeSH
Related in: MedlinePlus