Acquisition and carriage of meningococci in marine commando recruits

Meningococcal acquisition is a prerequisite for invasive disease. Three hun dred and eleven male marine commando recruits were studied throughout 29 we eks of basic training to identify factors influencing meningococcal carriag e and acquisition including troop number, season, smoking, respiratory infe ction, antibiotic usage and nasopharyngeal bacterial interference flora. A high carriage rate on entry to training (118/311, 37.9 %) and subsequent sustained high rates of meningococcal acquisition were found. Of the potent ial factors examined, only active and passive smoking were found to be asso ciated significantly with meningococcal carriage on entry. The association between active smoking and meningococcal carriage was dose-dependent, with odds ratios (OR) of 2.2 (95 % CIs 1.0-4.8) and 7.2 (95 % CIs 2.3-22.9) for light and heavy smokers respectively. Passive smoking predisposed independe ntly to carriage (OR 1.8, 95% CIs 1.1-3.0). Active and passive smoking comb ined to give an attributable risk for meningococcal carriage of 33 %. In co ntrast, despite a high and sustained rate of meningococcal acquisition in t he study population, none of the risk factors investigated, including activ e smoking, was associated significantly with meningococcal acquisition. No cases of meningococcal disease occurred during the 16-month study period. T herefore smoking may increase the duration of meningococcal carriage rather than the rate of acquisition, consistent with the increased risk of mening ococcal disease from passive as opposed to active smoking. Public health me asures that reduce the prevalence of smoking should reduce the risk of meni ngococcal disease.