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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.
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