STI diagnoses continue to rise in Scotland

On 26 May 2020, Health Protection Scotland (HPS), part of Public Health Scotland (PHS), published two reports revealing the numbers of sexually transmitted infections (STIs) recorded in Scotland between 2018 and 2019, specifically genital chlamydia, gonorrhoea and infectious syphilis. A third report, published by the Scottish Bacterial Sexually Transmitted Infection Reference Laboratory (SBSTIRL), contains information on antibiotic resistance to gonorrhoea.

Genital chlamydia remains the most frequently diagnosed STI in Scotland, with 17,336 diagnoses reported in 2019, which represents a 6% increase compared to 2018 (16,338). While laboratory confirmed diagnoses predominate in women (57% of all diagnoses), the number of diagnoses among men was the highest recorded in over 10 years (7,489). For the past decade, young people are the group most affected, with 64% of all diagnoses made in those aged less than 25 years.

In 2019, gonorrhoea diagnoses also increased with 3,776 diagnoses reported, indicating a 17% increase compared to the previous year. Using data from clinical records, this is the largest annual total recorded since the mid-1980s. In contrast to genital chlamydia, more than two-thirds (68%, 2,581) of gonorrhoea diagnoses were among men and, principally, among men who have sex with men (MSM), however, there has also been a steady increase in female diagnoses over the last four years. In women, infection with gonorrhoea is associated predominantly with a younger age group, with three-quarters (77%, 923/1,193) of female episodes occurring in those aged under 25 years. In 2019, rectal gonorrhoea, a marker of condomless anal intercourse (CAI), also remained high with the largest number of episodes recorded over the past decade.

Global public health concern continues around the emergence of gonococcal antibiotic resistance. The surveillance programme is critical to inform treatment and management guidelines, prevent treatment failure and control the spread of infection. In the UK, given the observed increase in recent years of the proportion of gonococcal isolates demonstrating high-level resistance to azithromycin (4.5% of all isolates in 2019), guidelines for gonorrhoea treatment changed in 2019 from azithromycin plus ceftriaxone dual therapy to ceftriaxone monotherapy.  Importantly, in 2019, no gonococcal isolates were resistant to ceftriaxone and there were no documented treatment failures.

In contrast to the observed increase in gonorrhoea and genital chlamydia infection, the number of diagnoses of infectious syphilis decreased by 20% between 2018 and 2019 (from 455 to 369), the first time a decrease has been recorded since 2015. The burden of infectious syphilis infection remains with MSM (86% of all diagnoses), however, heterosexual transmissions are also occurring.

While the decrease in diagnoses, primarily among MSM, is encouraging news, there is evidence of recent transmission of syphilis which is concerning as are the observed increases in rectal chlamydia and rectal gonorrhoea recorded among MSM in 2019, reaching the highest levels recorded in more than a decade. The impact of increased STI testing, particularly among MSM, associated with the successful implementation of an NHS-funded HIV pre-exposure prophylaxis (PrEP) programme in Scotland in July 2017 must be considered when interpreting these data. To assess the impact of the programme, now in its third year, HIV and other STI incidence continues to be monitored.

The findings of these reports highlight the continuing rates of unprotected sexual intercourse and the risk of STI infection, particularly among MSM, in Scotland in 2019. Furthermore, they underline the importance of a coordinated public health response, involving safer sex education and condom provision, regular testing and rapid access to treatment, and effective partner management, to meet the challenges for the control and prevention of STIs in Scotland.