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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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Related in: MedlinePlus

ACH and Estimated TB Risk under different ventilation conditions. Box-plot of ACH and estimated TB risk from the various ventilation conditions tested: (1) baseline with windows and door closed, (2) windows open, and (3) windows and door open. Mean ACH and TB risk for each condition is marked with “+”. Median ACH and TB risk is marked by the solid horizontal line, with the upper and lower ends of the box representing the limits of the interquartile range (IQR). The dotted lines represent the range of values. a. ACH b. Estimated TB Risk.
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Figure 2: ACH and Estimated TB Risk under different ventilation conditions. Box-plot of ACH and estimated TB risk from the various ventilation conditions tested: (1) baseline with windows and door closed, (2) windows open, and (3) windows and door open. Mean ACH and TB risk for each condition is marked with “+”. Median ACH and TB risk is marked by the solid horizontal line, with the upper and lower ends of the box representing the limits of the interquartile range (IQR). The dotted lines represent the range of values. a. ACH b. Estimated TB Risk.

Mentions: Among all homes, the mean ACH improved when windows were opened and improved further when windows and door were both opened (p < 0.0001) (Table 1, Figure 2a). Of note, there was no significant difference in ACH under closed conditions when any extra ventilating spaces, such as vents, remained open or were covered. Although there was no difference in baseline ACH, ventilation was more favorable in box-shaped metal roof homes than in round thatched roof homes as windows and door were opened (p = 0.01) (Table 1).


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)

ACH and Estimated TB Risk under different ventilation conditions. Box-plot of ACH and estimated TB risk from the various ventilation conditions tested: (1) baseline with windows and door closed, (2) windows open, and (3) windows and door open. Mean ACH and TB risk for each condition is marked with “+”. Median ACH and TB risk is marked by the solid horizontal line, with the upper and lower ends of the box representing the limits of the interquartile range (IQR). The dotted lines represent the range of values. a. ACH b. Estimated TB Risk.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: ACH and Estimated TB Risk under different ventilation conditions. Box-plot of ACH and estimated TB risk from the various ventilation conditions tested: (1) baseline with windows and door closed, (2) windows open, and (3) windows and door open. Mean ACH and TB risk for each condition is marked with “+”. Median ACH and TB risk is marked by the solid horizontal line, with the upper and lower ends of the box representing the limits of the interquartile range (IQR). The dotted lines represent the range of values. a. ACH b. Estimated TB Risk.
Mentions: Among all homes, the mean ACH improved when windows were opened and improved further when windows and door were both opened (p < 0.0001) (Table 1, Figure 2a). Of note, there was no significant difference in ACH under closed conditions when any extra ventilating spaces, such as vents, remained open or were covered. Although there was no difference in baseline ACH, ventilation was more favorable in box-shaped metal roof homes than in round thatched roof homes as windows and door were opened (p = 0.01) (Table 1).

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