Undiagnosed and missed active pulmonary tuberculosis during mass gatherings: a prospective cross-sectional study from the Hajj pilgrimage.

Mass gatherings increase the risk of infectious diseases transmission including tuberculosis (TB). The Hajj pilgrimage to Mecca, Saudi Arabia, is attended by over 2 million pilgrims many of whom are from high TB-burden countries, and has been linked to increased risk of TB acquisition among travellers. We investigated the burden of undiagnosed and missed active pulmonary TB (PTB) among Hajj pilgrims symptomatic for cough. The study was conducted among hospitalised and non-hospitalised travellers attending the Hajj pilgrimage in 2016 and 2017. Questionnaires were used to collect relevant data and sputum samples were collected from participants and processed using the Xpert MTB-RIF assay. Non-hospitalised pilgrims (n = 1510) originating from 16 high and medium TB-burden countries were enrolled. Undiagnosed, rifampicin-sensitive, active PTB was identified in 0.7%. Comorbidities (adjOR = 5.9 [95% CI = 1.2-27.8]), close contact with a TB case (adjOR = 5.9 [95% CI = 1.2-27.8]), cough in household (adjOR = 4.46 [95% CI = 1.1-19.5]), and previous TB treatment (adjOR = 10.1 [95% CI = 4.1-98.1]) were independent risk factors for TB. Of the hospitalised pilgrims (n = 304), 2.9% were positive for PTB, and 2.3% were missed, including a rifampicin-resistant case. History of TB treatment was associated with increased risk of TB (adjOR = 8.1 [95% CI = 1.3-48.7]). International mass gatherings may play an important role in the global epidemiology of TB. Preventive measures should be directed to reducing the risk of TB importation and transmission during Hajj and other similar events.