Table 1.

Model assumptions regarding the factors affecting the risk of transmission

	Modification in risk of transmission	Source
Affecting index infectiousness
Extrapulmonary TB	Not infectious	–
Smear-negative TB	One quarter as infectious as smear-positive cases	[19, 20]
Age	Infectiousness increases with age (see Additional file 1, Section 3.2)*	[21, 22]
Detection	The transmission probability is halved once the index case has been detected	Assumption
Affecting contact susceptibility
BCG vaccination	Reduces the risk of the vaccinee becoming infected. Vaccine immunity wanes over time (see Additional file 1, Section 3.2)	[23–25]
Current M.tb infection	Reduces the risk of novel infection (RR = 0.21)	[26]

*Assumption explored in sensitivity analysis