Smoking prolongs the infectivity of patients with tuberculosis.

We sought to establish if smokers on anti-tuberculosis treatment are more likely to have a prolonged period of infectivity, compared to non-smoking tuberculosis patients, in a low tuberculosis prevalence country. We conducted a cross-sectional, retrospective study in Ireland that recruited 53 microbiologically confirmed cases of pulmonary tuberculosis (PTB). The age-sex adjusted odds ratios (AOR) suggest that the infectivity status of PTB on treatment was four times more likely to be prolonged beyond 6-8 weeks, if the cases had a smoking history (AOR: 4.42; 95% CI: 1.23; 15.9). Smoking was associated with delayed sputum smear conversion in PTB patients on treatment.