A review of one hundred years of diagnoses of sexually transmitted infections (STIs) in the UK confirms that there have been sharp increases in gonorrhoea and syphilis since the historic lows of the 1990s, especially in gay and bisexual men. However, these rates do not as yet reach the historic high points for gonorrhoea and syphilis seen between the two world wars and in the 1970s.
The review by Dr Hamish Mohammed and colleagues from Public Health England and its equivalents in Scotland, Wales and Northern Ireland is published in the December issue of Sexually Transmitted Infections.
Placing STIs in their historic context – gonorrhoea
The authors place the post-AIDS increase in STIs within a historic context. Gonorrhoea cases in the UK have been recorded since 1918 and syphilis since 1922, when the UK’s network of free and confidential STI clinics was set up. This was after a Royal Commission on Venereal Diseases (as STIs used to be called) recommended a clinic network in 1916, partly as a response to alarming increases in the two diseases leading up to and during World War I.
The historic figures for gonorrhoea show that the 2015 and 2017 figures of around 45,000 cases of gonorrhoea are the highest total since 1986. However, the first time gonorrhoea diagnoses reached this figure was in 1928-1930. As the UK population has increased by 46% since 1930, this represented a much higher rate per head of population. Gonorrhoea diagnoses remained at about 40,000 a year throughout the 1930s, fell by about 20% during World War II, then peaked abruptly in 1946 to 54,000 as soldiers came home from the front.
The advent of antibiotics brought that figure down to about 20,000 during the 1950s but then both antibiotic resistance, and the new era of sexual freedom, led to gonorrhoea cases rising to over 60,000 cases during the 1970s, with an all-time high of over 64,000 a year between 1973 and 1977. Cases then began to fall rapidly and reached a historic low of 10,000 a year between 1993 and 1995.
However diagnoses started to rise again as soon as antiretroviral combination therapy for HIV became available. There was a period between 2004 and 2010 when diagnoses were contained below 20,000 a year, but they have more than doubled since then.
The epidemic curve for gonorrhoea, in other words, shows a complex interplay between behaviour, testing and antibiotic resistance. It is an adaptable organism that retains the capacity to outwit medications.
Placing STIs in their historic context – syphilis
The historic story of syphilis is a little simpler as the syphilis organism rarely develops antibiotic resistance. Between 1930 and 1945 cases ranged between 8000 and 16,000 a year, with the same 1946 peak as gonorrhoea, to over 20,000 cases. Cases then fell precipitously with the introduction of penicillin to a low of 700-800 cases in the late 1950s, before rising to a peak of about 3000 cases a year in the late 1970s. The ratio of male-to-female cases rose throughout the 1960s and 1970s, suggesting that male-to-male transmission was important in the pre-HIV era.
Cases then started to fall and reached a historic low of 280 in 1995, just before the advent of HIV combination therapy, with about a third of male cases being in gay men. There was a sudden doubling of cases in 2001, which was also the first year that cases in gay men formed more than 50% of male cases.
Since then cases have risen sixfold overall, to over 6,000, and tenfold in gay men, but only by 75% in women. Syphilis is 18 times more common in men than women.
Trends in recent years
STI clinic attendances rose by 17% from 1.9 million in 2013 to 2.2 million in 2017, including increases of 23.5% in women and 55% in gay and bisexual men. In 2013 gay and bisexual men formed 20% of male clinic attendees, rising to 29% in 2017.
However there has been a decrease in the proportion of people offered an appointment within 48 hours since 2011, and the authors comment that “there has been a worrying worsening of service access, especially for symptomatic patients and women.”
The increase in clinic attendance is part of a long-term pattern and figures have improved ever since access targets were introduced for STI clinics in 2006. Although gay and bisexual men form only 11% of all STI clinic attendees, 53% of all gonorrhoea and syphilis diagnoses were made in this group.
Gonorrhoea cases in gay and bisexual men fell by 22% between 2015 and 2016, from 23,000 to 18,000. Mohammed and colleagues attribute this to improved testing uptake in clinics that occurred in parallel with increasing HIV testing, and which “may have helped facilitate prompt identification and treatment of asymptomatic infection, reducing the likelihood of secondary transmission.”
However they rose again to 22,000 in 2017. The best we can say at present is that regular testing and correct combination antibiotic medication for gonorrhoea could potentially contain continued gonorrhoea transmission within the gay community, but that the ease with which the organism becomes resistant to antibiotics remains a concern.
Syphilis figures have not fallen, and they suggest that “more targeted, quarterly syphilis testing, especially in HIV-positive MSM, may be required to effect a reduction in syphilis incidence.”
Chlamydia and testing
Chlamydia is the most common STI by far, forming 53% of all STI diagnoses, and 83% of the bacterial STIs (chlamydia, gonorrhoea, syphilis). As chlamydia is asymptomatic in 50% of men and 75% of women, diagnosis rates are closely linked to testing rates, but specific testing for the Chlamydia trachomatis bacterium only started in the mid-1980s. Chlamydia diagnoses fell by 2% last year and over 10% since 2012. This may not reflect a real decline in infections but rather in testing: there was an 8% decline in chlamydia testing last year, the continuation of a decade-long trend.
Chlamydia is concentrated in young people, especially young women. About one in 40 women aged under 25 has chlamydia, nearly three times the rate in young men. Chlamydia and gonorrhoea are three times more common in young men aged 25 and under, and eleven times more common in young women, than in their older counterparts. Syphilis is also more common in younger women, but not in men.
HPV cases fall
One notable success in STIs in recent years has been the reduction in genital and anal warts following the introduction of the HPV vaccine among girls of secondary school age in 2008. Genital wart diagnoses in England fell by 72% in young women aged below 25 between 2009 and 2017. Interestingly, wart infections in young men have also fallen by 62% since 2009, even though school age boys have not received the vaccine, giving evidence of ‘herd immunity’. The UK’s Departments of Health finally decided to give the HPV vaccine to boys this year and have also started to offer it to older gay and bisexual men as a standard part of STI care.
Ethnicity and deprivation
One particular ethnic community in the UK has a higher rate of STIs than others – people of black Caribbean and mixed white/Caribbean ethnicity. Gonorrhoea, chlamydia and herpes rates are four times higher in this ethnic group than they are in UK white people and at least twice as high as in black Africans. Caribbean women are also 14 times more likely to have trichomoniasis, a bacterial STI that is otherwise uncommon.
The authors comment that these rates are historic, having persisted from Caribbean migration in the 1950s till the present day, and may reflect both network effects and economic inequality among this population.
The authors note the recent worsening of access to STI clinics. “Ensuring prompt access to those in need should remain a priority, especially given significant reorganisations in sexual health service provision and reductions in spend on services,” they say.
They note that there has been a pilot of online STI service provision using posted self-sampling kits. “This has the potential to increase access to testing,” they say, “but care must be taken to avoid exacerbating sexual health inequality through the ‘digital divide’; this is of particular concern for black and minority ethnic people from socioeconomically deprived areas.”
Mohammed H et al. 100 years of STIs in the UK: a review of national surveillance data. Sexually Transmitted Infections. doi: 10.1136/sextrans-2017-053273. December 2018. Abstract here.
See also Public Health England. Sexually transmitted infections and screening for chlamydia in England, 2017. Health Protection Report, 12(20): June 2018.