Nasopharyngeal Carriage of Neisseria meningitidis in 181 Hajj and Umrah Pilgrims in Türkiye: Pre- and Post-Travel Prevalence and Serogroup Distribution n

BACKGROUND Meningococcal carriage and serogroup distribution are closely linked to the epidemiology of invasive meningococcal disease. Mass gatherings such as Hajj and Umrah may alter carriage dynamics. Monitoring carriage before and after travel can inform vaccination strategies. This prospective observational study aimed to evaluate nasopharyngeal carriage of Neisseria meningitidis in 181 Hajj and Umrah pilgrims in Turkey. MATERIAL AND METHODS A total of 247 participants were enrolled before travel, and 181 participants provided paired pre- and post-travel samples. Paired nasopharyngeal samples were collected before departure and after return. Carriage and serogroups were identified by single-tube multiplex real-time polymerase chain reaction assay. Changes in carriage status were analyzed with McNemar's test. RESULTS Among 181 participants with paired samples, meningococcal carriage increased significantly after travel (8.2% vs 14.4%; McNemar χ²=9.76; P=0.002), with acquisition more frequent than loss (28 vs 9 cases; odds ratio, 3.11; 95% CI, 1.47-6.58). New acquisitions were predominantly due to non-vaccine serogroups, particularly serogroup B (15 cases) and serogroup X (8 cases). Among Hajj participants (n=112), carriage increased significantly (9.8% vs 18.7%; P=0.002), mainly driven by serogroup B, whereas no significant change was observed among Umrah participants (5.7% vs 7.2%; P=0.48). CONCLUSIONS Meningococcal carriage increased significantly after travel, particularly among Hajj pilgrims, with new acquisitions predominantly involving serogroups B and X. These findings highlight the potential role of non-vaccine serogroups in post-travel carriage and the need for continued surveillance.