Some 131 cases of syphilis were reported in Sweden in the first six months of 2007, which represents a rise of 75 percent on the first half of last year. Of these, 26 cases were women and 102 were men. Of the men, 59 were diagnosed in men who had had sex with another man, according to the figures from the Swedish Institute for Infectious Disease Control (Smittskyddsinstitutet).
"In the gay community, the rise is mainly due to anonymous sexual encounters," epidemiologist Inga Velicko told The Local.
"What we have seen in analysis of cases, and what doctors at sexual health clinics in Stockholm have observed, is that men in anonymous sexual encounters with other men have very low condom use.
Of the syphilis cases transmitted by homosexual sex, 68 percent were in the Stockholm region, with the Skåne region also quite badly affected. 80 percent are believed to have contracted syphilis in Sweden; in 2006, only 56 percent of syphilis contracted through gay sex had been contracted in Sweden.
Left untreated, syphilis can damage the heart, brain, eyes and bones, and can be fatal. Most cases can be treated with a course of antibiotics. Many of the men diagnosed with syphilis also carry other sexually transmitted infections.
"The anonymous contact makes it impossible to track the people with whom these men have had sex," said Velicko.
The number of heterosexual transmissions of syphilis fell. In the first six months of this year, 14 men contracted the disease through sex with women, compared to 17 in the first six months of 2006. Five women were infected, compared to six in the same period last year. For both heterosexual men and women, most cases of syphilis were contracted abroad.
Chlamydia also rose dramatically in the first half of 2007. Most transmission was heterosexual, while the largest rise was among the 15-19 age group, in which cases were up 72 percent.
During the period, 22,610 cases were reported, an increase of 52 percent compared with the first half of last year. This was largely due to better diagnosis of a new variant of the disease discovered in Sweden in the autumn of 2006, and more people coming forward for testing, but there remains concern that infections among young people in particular continue to rise.
"We will be able to say for sure at the end of the year whether chlamydia has risen, but it seems that there is increased incidence in the 15-24 age group due to low condom use and large numbers of sexual partners," Velicko said.