When comparing estimated tuberculosis disease incidence rates to the estimated background incidence rate of 681 cases per 100,000 per year in the Western Cape [25], the estimated risk of tuberculosis disease is 3.3 fold higher overall, and is 4.1-fold and 2.7-fold higher than background incidence rates in TNF-α and non-TNF-α biologic therapies respectively. Here, TNF is linked to tuberculosis.