Management of asymptomatic sexually transmitted infections in Europe: towards a differentiated, evidence-based approach

Abstract

Most sexually transmitted infections (STIs) can be accurately diagnosed and treated during asymptomatic carriage. Widespread screening for these STIs is therefore assumed to be an effective way to reduce their prevalence and associated disease. In this review, we provide evidence that this is the case for HIV and syphilis. However, for other STIs such as Neisseria gonorrhoeae and Chlamydia trachomatis, our review reveals that the evidence that screening reduces infection prevalence and associated disease is weak. There is also growing evidence of harms from screening that might outweigh any benefits. The harms include the increased consumption of antimicrobials that follows frequent screening and increased detection of asymptomatic STIs in key populations, such as men who have sex with men taking HIV pre-exposure prophylaxis, and associated risk of antimicrobial resistance in target and non-target organisms. There may also be psycho-social harm associated with an STI diagnosis. We conclude that in the absence of symptoms, in high STI prevalence populations frequent STI screening should be limited to HIV and syphilis.

Fig. 1

A schematic illustration of a number of ways that STIs can circulate asymptomatically in a population. (A) The majority of infections of certain STIs such as herpes simplex virus-2 (HSV-2) do not produce any symptoms. After a latent period, the HSV-2 does, however, become infectious (red line), before returning to latency in the dorsal root ganglia. It can then reactivate and become infectious again (with or without symptoms) for multiple periods for the following decades. (B) The vast majority of anorectal and pharyngeal N. gonorrhoeae, C. trachomatis and M. genitalium infections are asymptomatic and self-resolving. (C) For an STI such as mpox, the symptomatic and infectious periods are short, but the period of infectiousness begins before the symptomatic period (blue ovoid shape). Individuals can transmit the mpox virus in this presymptomatic period.

Fig. 2

Prevalence of N. gonorrhoeae, C. trachomatis and M. genitalium in a typical PrEP cohort in Belgium. Participants were screened at 3-sites (pharynx, anorectum and urethra) every three months for each of these STIs.

Fig. 3

An illustration of the connection between sexual network connectivity and equilibrium prevalence of N. gonorrhoeae and C. trachomatis using data from the ANRS-Prevenir study of PrEP in France. The relatively high rate of partner turnover (15–20 partners per 3 months) generates a dense sexual network (black arrows), which in turn, sustains a high equilibrium prevalence/incidence (blue arrows) of both N. gonorrhoeae and C. trachomatis (between 30 and 50 infections per 100 person years).