Increased transmission and incidence of syphilis in southern Sweden 2007-2022

Syphilis has re-emerged as a public health threat during the 21st century, and updated knowledge of the epidemic and its drivers is needed to halt this worrying development. We present data on the incidence of syphilis in the south Swedish region Skåne from 2007 to 2022 to determine the burden of disease, changes in risk groups, as well as routes for testing. To get a picture of the burden of syphilis, both early (notifiable) syphilis and cases of non-notifiable (late) symptomatic syphilis were included in this register-based study. Mann-Kendall trend analysis (MK) was used to determine statistical significance over time. In all, 584 cases of syphilis were included in the study. The overall syphilis incidence in Skåne increased from 3.1 cases/100000 population in 2007 to 6.3 in 2022 (MK z-stat: 2.57; p = 0.010). The highest increase in absolute numbers was among men who have sex with men (MSM), from eight cases annually in 2007 to 62 in 2022, but also for heterosexually transmitted men and women, with under ten cases yearly from 2007 through 2019 to 22 cases in 2022. We also found that transmission within Sweden was common, indicating that local measures are needed to curb this epidemic.