In 2015, there were 434,456 new STI diagnoses made at SHCs in England. Of these, the most commonly diagnosed STIs were chlamydia (200,288; 46%), genital warts (first episode; 68,310; 16%), non-specific genital infections ([NSGI] 42,262; 10%), and gonorrhoea (41,193; 10%).
Compared to 2014, the total number of new STIs diagnosed in 2015 decreased by 3% (434,456 vs. 449,642). This is mostly explained by a decrease in the number of chlamydia diagnoses between 2014 and 2015 (4%; from 208,638 to 200,288). Most of the decrease in chlamydia diagnoses was due to a decrease in diagnoses from community-based settings (7%; 99,785 to 93,036).
It may also be due to the reduction in heterosexual women testing in communitybased settings, which could have had the effect of reducing the number of male partners attending for testing and treatment at specialist SHCs. A marked decrease in genital warts diagnoses between 2014 and 2015 (7%; from 73,086 to 68,310) also contributed to the overall decline in new STIs. Most of this is explained by a reduction in genital warts diagnoses in 15-19 year old females over the same time period (13%, from 7,921 to 6,878) associated with Human Papillomavirus vaccination. This and recent trends in genital warts are discussed in an accompanying article of this issue of the HPR .
Lastly, a reduction in NSGI diagnoses (10%; 47,183 to 42,262) also contributed to the overall decline in new STIs. This is consistent with the decline in NSGI reported since 2012 and may be due to the increasing use of nucleic acid amplification tests (NAATs) to detect chlamydia and gonorrhoea.
However, between 2014 and 2015, there were increases in diagnoses of syphilis ([primary, secondary and early latent stages] 20%; 4,412 to 5,288) and gonorrhoea (11%; 37,100 to 41,193), continuing the increasing trend in these infections seen in recent years: since 2012, syphilis diagnoses have risen by 76% (3,001 to 5,288) and gonorrhoea by 53% (26,880 to 41,193). These increases were maintained after adjusting for the corresponding increase in attendances at SHCs over the same period (17%; 2,616,730 to 3,055,385), as diagnosis rates per 100,000 attendances rose by 51% (114.7 to 173.1) for syphilis and 31% for gonorrhoea (1,027.2 to 1,348.2) from 2012 to 2015. Most of the increases in diagnoses of both infections are in men who have sex with men (MSM), the possible reasons for which are discussed in the following section of this report (Men who have sex with men).
Over the past decade, diagnoses of gonorrhoea, syphilis, and genital herpes have increased considerably, most notably in males, while diagnoses of genital warts have decreased in females (figure 1). Since the full scale implementation of the NCSP in 2008, diagnosis rates of chlamydia have also increased in men and women. More STI testing in SHCs and through the NCSP  and routine use of more sensitive diagnostic tests, such as NAATs, partly explain these increases, although ongoing unsafe sexual behaviour has contributed. Chlamydia and genital warts diagnoses are discussed in later sections of this report (Genital Chlamydia trachomatis tests and diagnoses in young people and Young heterosexuals and STIs).
Reliable data on the sexual orientation of patients is available from SHCs’ GUMCADv2 data returns. Among diagnoses made in these settings, there is substantial variation in the distribution of the most commonly diagnosed STIs by gender and sexual orientation. Men who have sex with men accounted for 79% of syphilis and 54% of gonorrhoea diagnoses, while heterosexual men and women accounted for 92% of genital warts, 92% of genital herpes and 85% of chlamydia diagnoses. Among heterosexuals, twice as many women as men were diagnosed with genital herpes.