Sexually transmissible infections and sexual risk behaviour among deployed, ship-assigned USA Navy and Marine Corps personnel

Background Data show sexually transmissible infection (STI) diagnoses in USA military personnel engaging in unprotected sex are higher during deployment than before or after. We examined sexual risk behaviour, same-sex contact, mixed sex partnerships (both casual and committed partners) and STIs among ship-assigned USA Navy and Marine Corps personnel to assess increased risk.Data on sexual risk behaviour, partner type, gender, and healthcare provider-diagnosed STIs were collected longitudinally (2012-14) among sexually active personnel during deployment. Descriptive and bivariate data stratified by sex, STIs, and partner types were analysed using χ2 and t-tests, with statistical significance defined as P < 0.05.The final sample (n = 634) included 452 men (71%) and 182 women (29%). STI prevalence among males was 8% (n = 36); men who have sex with men (MSM) accounted for 25% of total STIs, and 43% of MSM reported an STI. Among all reporting STIs, 29% reported occasional partners, service member partners (15%) and non-condom use (16%). The highest proportions of non-condom use (71%), alcohol before sex (82%), and same-sex partners (67%) were reported by participants with mixed sex partners; 69% of these reported service member partners.Personnel with mixed partners reported high proportions of sexual risk behaviour. MSM accounted for 9% of the total population, but 25% of all STIs. As the majority of those with mixed partners and MSM also reported service member sex partners, safer sex education and prompt STI identification/treatment among these groups could reduce STI transmission among military personnel.