A nationwide sentinel clinic survey of chlamydia trachomatis infection in Finland.

BACKGROUND: Chlamydia trachomatis has been recognized as a major sexually transmitted infection in North America and Western Europe during the past two decades. The incidence of C trachomatis in Finland has been continuously high throughout the 1990s. OBJECTIVES: As the epidemic of C trachomatis infection continues in Finland, there is a need to obtain up-to-date information on the prevalence and patient profiles in the planning of preventive strategies. METHODS: A nationwide sentinel clinic network consisting of seven sexually transmitted disease (STD) and five general student health clinics was established in 1995. Data were collected during a 3-year period (1995-1997) from 3,686 patients with and 32,230 patients without C trachomatis using a self-administered questionnaire. RESULTS: The prevalence of chlamydia was 8.4% in the STD clinics and 5.3% in the general clinics; 90% of the infections were endemic. The prevalence was highest in the youngest age group (15-19 years; 16% in females, 14% in males). The patients with chlamydia were significantly younger (mean age: men 26.6 years, women 23.7 years) than those without chlamydia. Women with chlamydia used oral contraceptives or intrauterine devices (IUD) significantly more often (59%) than women without chlamydia (42%). A high number of sex partners and a history of previous chlamydia during the preceding 12 months were also risk factors. Men contracted chlamydia frequently from a casual partner (61%) but rarely from a commercial sex worker (2%). For women, the source partner was most often a regular one (61%). The median time from exposure to attendance was 34 days, and was highest when the source partner was a spouse. One third of the patients could have spread chlamydia to a new partner before the diagnosis. CONCLUSIONS: C trachomatis infection is spread all over Finland, and the risk factors include younger age, high number of sex partners, and use of oral contraceptives or IUDs. Source partner analysis focused attention on the importance of transmission from regular partners, especially in women. The time from transmission to diagnosis was long, and any effort to shorten this period would be an effective preventive strategy.