Table 1 Model assumptions regarding the factors affecting the risk of transmission

 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

 BCG vaccination

Reduces the risk of the vaccinee becoming infected. Vaccine immunity wanes over time (see Additional file 1, Section 3.2)

[23,24,25]

 Current M.tb infection

Reduces the risk of novel infection (RR = 0.21)

[26]