Syphilis 2021

Syphilis 2021

The present report on notified syphilis cases in 2021 only comprises data from the Notification System for Infectious Diseases (NSID).

In 2021, 634 syphilis cases were notified to the NSID, Department of Infectious Disease Epidemiology and Prevention (DIDEP), Statens Serum Institut (SSI); 582 cases among men and 52 cases among women. The 634 cases occurred in 622 persons as 12 persons were notified with two cases in the course of the year.

The median age was 37 years for men (range 16-75 years) and 37 years for women (range 16-62 years), Table 1.


As in previous years, the majority of the patients resided in the Copenhagen area, Table 2.


The incidence increased considerably in the City of Copenhagen and in North Zealand in 2021 compared with 2020.


The decline registered in 2018 when the number of notified syphilis cases was 311 has been replaced by an increase since 2019. The increase is mainly seen among men who have sex with men (MSM), Figure 1.

Congenital syphilis and syphilis in pregnant women

Among 52 cases of syphilis detected in women in 2021, nine (17%) were found in pregnant women, five of whom were Danish born. In 2021, the pregnancy screening efforts confirmed a total of 15 female syphilis cases. Thus, six pregnant women with syphilis (40%) had not been notified to the NSID.

No cases of congenital syphilis were notified in 2021.


Sexual orientation

Among the 582 notified men, 81 (14%) were notified as having become infected by heterosexual contact (HTX), 493 (85%) by MSM contact, and for eight (1%) the mode of infection was not stated.

A total of 52 women were notified; 51 had become infected by HTX, and for one woman the mode of infection was not stated. In 2021, women comprised 8% of all notifications, Figure 1.

Origin and country of infection

Among the 634 notified cases, 417 (66%) were born in or had been adopted to Denmark, and 217 (34%) were immigrants, tourists, etc.

The country of transmission was stated for 588 (93%) of those notified; 539 men and 49 women. A total of 502 men (93%) and 46 women (94%) had become infected in Denmark. Among HTX-infected men for whom the country of transmission was stated, 67 of 75 (89%) had become infected in Denmark, whereas this was the case for 430 of 459 (94%) of the MSM.

Syphilis and HIV

Information about HIV status was available for 593 (94%); 546 men (94%) and 47 women (90%).

Among the 465 MSM for whom HIV status was stated, 102 (22%) were HIV positives. All were previously known to be HIV positives. Thus, in 2021, no-one received their HIV diagnosis when receiving their syphilis diagnosis. No HTX-infected men or women were notified as HIV positives.

(L.H. Holm, S. Cowan, Department of Infectious Disease Epidemiology and Prevention)

This report is described in EPI-NEWS 49-50/2022.