International travel as risk factor for Chlamydia trachomatis infections among young heterosexuals attending a sexual health clinic in Melbourne, Australia, 2007 to 2017

Background: International travel is considered a risk factor for acquiring Chlamydia trachomatis; however, there are little empirical data to support this. Aim: To examine the prevalence and risk factors for Chlamydia trachomatis infections among heterosexual international travellers (n = 28,786) attending the Melbourne Sexual Health Centre (MSHC), Australia, compared to Australian residents (n = 20,614). Methods: We conducted a repeated cross-sectional study and analysed sexual behaviours and chlamydia positivity among heterosexual males and females aged <= 30 attending MSHC for the first time between January 2007 and February 2017. 'Travellers' were defined as individuals born outside of Australia who had resided in the country < 2 years. Associations between patient characteristics and chlamydia positivity were examined. Results: Chlamydia positivity was higher among travellers (11.2%) compared with Australian residents (8.5%; p < 0.001). Male travellers had higher chlamydia positivity (12.1%) than Australian males (9.3%; p < 0.001), as did female travellers (10.4%) compared with Australian females (7.7%; p < 0.001). Travellers had a higher mean number of sexual partners than Australian residents among males (5.7 vs 4.7; p < 0.001) and females (3.6 vs 3.2; p < 0.001). Travellers from the United Kingdom, Europe, Ireland and New Zealand accounted for 29.6%, 21%, 8.5% and 5.8% of C.trachomatis infections, respectively. Chlamydia in males and females was associated with younger age (<= 25), inconsistent condom use, a higher number of sexual partners (>= 4 partners) and being a traveller (p < 0.001). Conclusions: We found that international travel is an independent risk factor for chlamydia among young heterosexual travellers in Australia, who should therefore be a target group for chlamydia prevention.