Background Many studies show, STIs have a closed relation with HIV. STI increases the risk of getting HIV, HIV infection makes STIs more difficult to diagnose, treat. From 2011–2012, STI services were provided to most-at-risk populations (MARPs) in 8 provinces in Vietnam by the support from CDC/PEPFAR. The MARPs included commercial sex workers (CSWs), men have sex with men (MSM) and injecting drug users (IDUs).

Method A descriptive cross sectional study of 5187 MARPs in 8 provinces in Vietnam was undertaken from 10/2011–9/2012 to determine the prevalence of STIs in specific MARPs.

Results Among 5187 MARPs screened for STIs, 4,119 MARPs (79.4%) had STIs. Among STIs patients recorded, CSW had the highest proportion (83%), followed by IDUs (16%) and MSM only 1%.

Among STI patients, 59.7% (n = 2461) were diagnosed by syndromic approach and 40.3% by etiologic approach. In the group of syndromic diagnosis: Among 2,105 CSWs recorded, 51.7% had vaginal discharge and 7.9% had genital ulcer. Among 353 IDUs, 89.4% had urethral discharge and the proportion of genital ulcer was accounted for only 0.6%. Regarding MSM, all of them have urethral discharged (n = 3).

In the group of etiologic diagnosis: Among 1,313 CSWs tested to detect STI, 28.9% (n = 379) had bacterial vaginitis, 22.7% (n = 298) had vuvovaginal Candidiasis, 2.2% (n = 30) had genital Chlamydia infection, and 1.2% (n = 16) had vaginal Trichomoniasis. 26.9% (n = 352) of the CSWs had genital wart. Among 303 IDUs, 32.6% (n = 100) had genital wart, 17.9% (n = 55) had gonorrhoea and 11.1% (n = 41) had genital HSV infection. Among 42 MSM, 85.7% (n = 36) had genital warts and, 7.1% (n = 3) had gonorrhoea.

Conclusion Vaginal discharge syndrome was the most common syndrome among CSWs, urethral discharge was the most common syndrome among IDUs. Among CSWs, the most common STIs were bacterial vaginitis, HPV. Among IDUs and MSM, the most common STIs was HPV.