Carina Jonasson, Göran Bratt and Sven Grützmeier

Affiliates

Department of Infectious Diseases/Venhälsan, South General Hospital, Stockholm, Sweden

Abstract

Background: Syphilis is a sexually transmitted infection (STI) well known since the end of the fifteenth century. Modes of transmission are mainly through sex, contact with primary lesions and mother-to-child transmission. Syphilis is clinically divided in four stages, primary, secondary, tertiary and latent. With the arrival of the HIV-infection in the 1980’s, syphilis became nearly extinct in Sweden because of safe sex routines among MSM. After the introduction of modern antiretroviral therapy (ART) for HIV-infection in 1996 condom use has diminished and STIs increased. From 1998 we and several others have noticed an increase in syphilis infections, especially among HIV-positive MSM. The aim of this study is to describe the outbreak stratified by HIV status.
Methods: All MSM investigated for STIs at our clinic from 1998 to 2017 we included in the study. Routine STI investigation includes test for gonorrhea and chlamydia from throat, urethra/urine and rectum, clinical examination and blood tests for syphilis and HIV. Since 2011 all our HIV-positive MSM have syphilis tests once a year. We used the venereal disease research laboratory (VDRL) test and Treponema pallidum particle agglutination assay (TPPA) test.
Results: A total of 1230 cases were included in the study. Annual number of patients increased from 1 in 1998 to 158 in 2017 and 30% were reinfections. Median age was 40 years (IQR 33-48). The proportion of reinfections increased during the study period. The majority of infections (61%) were contracted in Sweden. In 21% of the cases, the patient was concomitantly diagnosed with at least one other STI. Chlamydia was the most common (12%). A new HIV-infection was diagnosed in 5% of the syphilis patients. The proportion of HIV-positive patients increased from 29% during the first five years of the study to 50% during the last five years. Primary syphilis was the most common stage at diagnosis, accounting for 42% of the cases, secondary 22%, and latency 36%. Primary infection was penile in 56% of the cases, anorectal in 29% and oral in 15%. There was no significant difference between patients with and without HIV-infection regarding concomitant STIs apart from Lymphogranuloma venereum and hepatitis C, which were more common in HIV-positive individuals. Reasons for investigating STI was symptoms in 56%, routine testing 25% and partner notification 19%. Secondary syphilis was more common in patients with HIV infection as was a higher VDRL titer. Reinfections were also more common in patients with HIV-infection. Of the HIV-negative patients with a new syphilis 12.5% seroconverted to HIV infection. The median time between the first syphilis episode and HIV seroconversion was 30 months.
Conclusions: The incidence of syphilis has increased in the MSM group during the last 20 years, especially in MSM with HIV-infection. MSM with HIV-infection have more often secondary syphilis and also lymphogranuloma and Hepatitis C compared to MSM without HIV infection. Syphilis detection by routine control has increased since we started yearly testing for syphilis and other STIs in MSM with HIV. All MSM with more than one partner should have at least yearly STI controls irrespective of HIV-status. Syphilis infection in MSM without HIV-infection is a warning sign of future HIV-infection and this should be discussed with the patients and indications for PrEP. More knowledge of syphilis, the symptoms, and the ways it is contracted as well as how to prevent it, is needed among patients and physicians.