There were just under half a million new diagnoses of sexually transmitted infections (STIs) in 2012, according to data released by Public Health England today. As in previous years, there were particularly high rates in gay men and in young heterosexual adults, with some urban areas having a much greater burden of disease than other parts of the country.
More encouragingly, rates of genital warts are down in young women – apparently because of HPV vaccination.
The total number of diagnoses is a little higher than the previous year (from 428,255 to 448,422 in 2012). Chlamydia remained the most commonly diagnosed infection (206,912 diagnoses), but there were also many diagnoses of genital warts (73,893), non-specific genital infection (59,942), genital herpes (32,021) and gonorrhoea (25,525). In comparison, the number of syphilis infections was much lower (2978).
Gay men have a disproportionate burden of some STIs. In sexual health clinics, 79% of men diagnosed with syphilis and 58% of men diagnosed with gonorrhoea are gay men and other men who have sex with men (MSM).
The headline figures suggest dramatic increases in gonorrhoea and chlamydia infections in recent years in MSM. For example, there were 4578 diagnoses of gonorrhoea in 2010, 7465 in 2011 and 10,205 in 2012.
However, the way in which these infections are diagnosed has changed in recent years, with more sensitive tests probably contributing to the increasing number of infections identified. Nucleic Acid Amplification Tests (NAATs) are now recommended and more tests are performed on samples from the throat and rectum, rather than only testing genital samples.
Nonetheless, the Public Health England epidemiologists judge that “ongoing high levels of unsafe sex among MSM are likely contributing to increased transmission”. Moreover, gonorrhoea rates are of particular concern due to the increasing prevalence of drug-resistant gonorrhea that does not respond to existing antibiotics.
Young people aged 15 to 24 years experience the highest rates of STIs. Among heterosexual people diagnosed in sexual health clinics, 64% of those with chlamydia were in this age group, as were 54% of those with genital warts, 55% with gonorrhoea, and 43% with genital herpes.
While chlamydia screening has reached large numbers of young people (1.7 million tests in 2012, equivalent to around 35% of young women and 16% of young men being tested during the year), Public Health England points to different testing rates in different parts of the country. It believes that regional differences in the number of chlamydia diagnoses are primarily driven by variations in the availability of screening (rather than risk behaviour). PHE urges local areas with lower rates of diagnoses to improve their promotion and delivery of chlamydia screening.
There are higher rates of STIs in people of black ethnicity, compared to other ethnic groups. In black people, there were approximately 2292 diagnoses for each 100,000 people in the population. This contrasts with 535 diagnoses per 100,000 people of white ethnicity, 380 per 100,000 in people of Asian ethnicity, and 1380 per 100,000 people of mixed ethnicity.
Public Health England says that infections in black people are especially concentrated in individuals living in deprived urban areas.
HPV vaccination and genital warts
Encouragingly, the report suggests that HPV vaccination could be having an impact on infection with genital warts. While overall diagnoses in the under 25s are greater than a decade ago, there has been a recent decline in cases of genital warts in women aged 15 to 19 (falling by 22% from 11,276 in 2009 to 8770 in 2012).
The authors say that several factors could contribute to this decline. However, they say there is new evidence that the vaccine Cervarix (which was designed only to protect against HPV 16 and 18, the types associated with cervical and anal cancers) does in fact also have a modest protective effect against HPV 6 and 11 (the types associated with genital warts).
Cervarix was provided in England from 2008 to 2012, when it was replaced by Gardasil (which offers strong protection against all four types of HPV). Hopefully the new vaccine will bring down genital warts rates further.
Data from Australia, where Gardasil has been provided to young women and girls since 2007, suggest that this is possible – in four years, genital warts declined by 93% in women under 21, and by 82% in heterosexual men under 21 (who benefit from their female partners' lack of infection). During the same time period, rates stayed stable in those aged over 30 and in gay men, who did not participate in the vaccination programme.