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Table 1 ACH and estimated TB risk in predominant home types

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

 

All homes

Box-shaped, Metal-roofed

Round-shaped, Thatch-roofed

 

ACH

Mean (SD)

Mean (SD)

Mean (SD)

p-value

  Closed

3 (2.9)

3 (2.7)

3 (3.3)

0.50

  Windows Open

9 (7.1)

13 (8.1)

5 (2.9)

0.01

  Windows & Door

20 (13.1)

27 (9.7)

13 (12.8)

0.01

  Open

*TB Risk (10h exposure)

    

  Closed

55.4 (27.8)

58.3 (24.7)

52.5 (31.5)

0.62

  Windows Open

21.5 (14.1)

24.7 (18.1)

18 (8.4)

0.32

  Windows & Door

9.6 (4.7)

8.9 (3.6)

10 (5.6)

0.44

  Open

  1. SD standard deviation.
  2. Wells Riley equation: C = S(1 − e − Iqpt/Q) where C = number of new cases, S = number of susceptible individuals, I = number of infectors (presumed to be 1 per household), q = number of infectious quanta produced per hour per infector (assumed to be 13 based on previous studies) [22], p = pulmonary ventilation rate of susceptible individuals (0.6 m3/h, previously established), t = exposure time of susceptible individuals, Q = absolute room ventilation (ACH*room volume). The probability of a new case was C/S.