Figure 3A&B.

The mean annual risk of TB infection for a child visiting 1 to 3 households other than own residential household during the day each with (Figure A) ventilation of 2 air changes per hour and (Figure B) ventilation of 6 air changes per hour. Values are plotted for mean periods of adult TB infectivity (delta, Δ) of 30, 60, 90 and 120 days.

N.B. The period of infectivity (delta, Δ) is the time from onset of infective tuberculosis until initiation of effective antituberculosis chemotherapy. Modeled estimations are for a pre-school child spending 75% of day-time indoors, a median of 2.2 resident adults per visited shack, a 1.35% annual risk for smear-positive tuberculosis and a mean production of 1 infectious air-borne quantum of TB per hour during untreated smear-positive disease.