Epidemics due to imported syphilis in Finland.
BACKGROUND: Russia and other states of the former Soviet Union experienced a huge increase in syphilis beginning in the early 1990s. At first these epidemics were not well known in neighboring countries such as Finland. STUDY DESIGN: In 1995 the incidence of syphilis in Finland doubled to 3.3/100,000 and a local cluster of 18 cases was detected in the city of Tampere. The reasons for this epidemic were analyzed and the occurrence of syphilis was carefully monitored up to 2001. RESULTS: The main reason for the increased incidence in Finland was the import of syphilis from Russia; only a few cases were acquired from Estonia or elsewhere. The source partners of Finnish men who contracted syphilis abroad were mostly sex workers or other casual partners. Mobile prostitution to Finland was not involved in the transmission. Most syphilis cases were found sporadically in southern Finland, in areas where foreign travel is frequent. Secondary transmission in Finland was usually limited to one or two partners. The only isolated cluster was further away and developed due to unawareness of the risk of syphilis by the cases and local healthcare providers. From 1995 onward, syphilis was carefully monitored by national reporting and a special sexually transmitted disease (STD) surveillance network, and the incidence remained at a constant level even though travel to and from Russia more than tripled. Nationwide serologic surveillance in STD and maternity clinics and among blood donors showed no major changes in the prevalence of syphilis. CONCLUSION: An epidemic of syphilis imported mainly by heterosexual men from Russia caused one sporadic cluster in Finland in 1995. Thereafter, general awareness by the public and healthcare providers about the risks of contracting syphilis from abroad, in addition to effective use of national surveillance and notification systems, was needed to protect the country from further spread of syphilis to an endemic infection.