Syphilis 2023
Annual Report on Syphilis 2023
This report on syphilis cases in 2023 includes only data from the Notification System for Infectious Diseases (MIS).
In 2023, 649 cases of syphilis were reported to MIS, Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut. Among these, there were 569 cases among men, 76 among women, two among trans women, and two among trans men. In this report, trans women are categorized under women and trans men under men.
The 649 cases were distributed among 638 individuals, as 11 individuals were reported with more than one case throughout the year. In total, 157 of the cases reported in 2023 were among individuals who had previously been reported with syphilis (including the 11 reported with multiple cases in 2023). Several individuals were reported with syphilis repeatedly, up to eight times.
The median age for men was 41 years (range 15-79 years), and for women, 37 years (range 17-64 years), Table 1.
As in previous years, the majority of patients resided in the Copenhagen area, Table 2.
The decrease observed in 2018, when the number of reported syphilis cases reached 311, has since been replaced by an increase beginning in 2019. This rise was mainly observed among men who have sex with men (MSM), but this group has shown a decline from 2021 to 2023, Figure 1.
Congenital Syphilis and Syphilis Among Pregnant Women
Among the 78 women reported in 2023, eight (10%) were reported as pregnant, six of whom were born in Denmark. In prenatal screening, a total of 10 women were confirmed to have syphilis in 2023, meaning two pregnant women with syphilis (20%) were not reported to MIS.
No cases of congenital syphilis were reported in 2023.
Transmission Factors
Sexual Orientation
Among the 571 reported men, 121 (21%) were reported as infected by women (heterosexually transmitted, HTX), 427 (75%) were reported as infected by men (MSM), and 23 (4%) were reported without information on transmission mode. All 78 reported women were infected by men.
Country of Transmission
Country of transmission was specified for 613 (94%) of those reported. Apart from Denmark, where 538 cases (88%) were contracted, infections were most commonly acquired in Germany, Thailand, Spain, and the USA.
Syphilis and HIV as well as PrEP Treatment
HIV status was available for a total of 561 individuals (86% of reported cases); among the 427 men infected by men, this information was available for 396 (93%), for the 121 men infected by women, it was available for 92 (76%), and among the 78 women, HIV status was available for 61 (78%).
A total of 110 cases also involved HIV; 103 known and seven newly diagnosed. Among the 396 men infected by men, 105 (26%) were also HIV-positive; 98 known and six newly diagnosed. Among the 92 men infected by women, two individuals (2%) had known HIV, and among the 61 women, there was one case of known HIV and one newly diagnosed HIV case, the latter in a trans woman.
Among the 451 reported as HIV-negative, 119 were on so-called PrEP treatment (Preexposure Prophylaxis, i.e., medication taken preventatively against HIV), the majority being MSM.
This report is also discussed in EPI-NEWS 42-43/2024