Epidemiology of STIs: UK

EPIDEMIOLOGY AND SEXUAL BEHAVIOUR

Epidemiology of STIs: UK

Historical data Data on syphilis and gonorrhoea have been collected for more than 80 years. Diagnoses of syphilis and gonorrhoea in England, Scotland and Wales peaked in 1946, coinciding with the return of the armed forces after World War II (Figure 1). There was a sharp decline immediately thereafter, associated with the introduction of penicillin and the return to social stability. More relaxed attitudes to sexual behaviour during the 1960s and 1970s heralded a steady increase in diagnoses of STIs. Syphilis diagnoses in males increased, whereas the number of cases in females remained constant, suggesting sex between men became the major route of acquisition of syphilis during this period.7 However, diagnoses of gonorrhoea, genital herpes and genital warts increased in both males and females, indicating that these infections were more commonly acquired through heterosexual sex. For some of these STIs, the increases may reflect greater public awareness and/or improved diagnostic sensitivity, in addition to greater incidence of infection. The emergence of HIV and AIDS in the early 1980s is now believed to have had a significant impact on the incidence of other acute STIs. Diagnoses of syphilis and gonorrhoea declined sharply in the early to mid-1980s, coinciding with extensive media coverage of AIDS, adoption of safer sex practices, and a subsequent decrease in HIV transmission among male homosexuals.8 Similarly, the number of diagnoses of genital herpes and genital warts, both of which had increased steadily since 1972, stabilized (and in the case of herpes, decreased briefly) during the mid-1980s. These changes are likely to be associated with general population-level behavioural modification in response to the HIV/AIDS epidemic.

Catherine M Lowndes Kevin A Fenton

Public health importance As highlighted in the Department of Health’s National Strategy for Sexual Health and HIV,1 STIs are a major public health concern. They place a significant burden on health-care resources both directly, through individuals seeking treatment and care, and indirectly, resulting from management of the complications of untreated disease (including pelvic inflammatory disease, infertility, ectopic pregnancy and cervical cancer). The epidemiology of STIs in the UK showed remarkable changes over the 20th century, reflecting changes in sexual behaviour, new diagnostic techniques and social, economic and demographic shifts within society.2,3,4

Surveillance Genitourinary medicine (GUM) clinics provide the most comprehensive source of data on the epidemiology of STIs in the UK.4 In England, Wales and Northern Ireland, statutory KC60 statistical returns submitted by all clinics provide aggregate data on total numbers of episodes of diagnosed STIs by sex and age group (and sexual orientation for selected conditions). Further information is obtained from voluntary laboratory reporting and via patientbased enhanced surveillance systems, including the Enhanced Syphilis Surveillance system5 and the Gonococcal Resistance to Antimicrobials Surveillance Programme.6 In Scotland, the ISD(D)5 returns system provides anonymous individual data on all STI diagnoses in GUM clinics. (Data from GUM clinics are currently unavailable for Scotland for 2001, 2002 and 2003, and therefore this contribution focuses on England, Wales and Northern Ireland when discussing recent trends in reported diagnoses from GUM clinics. When possible, recent data from laboratory reports are included for Scotland.)

Recent trends The decline in STI diagnoses that occurred in the mid-1980s was maintained until the early 1990s. Since then, however, there has been a resurgence in diagnoses of many STIs, and the number of diagnoses has increased considerably since 1995 (Figure 2).4 The trend has been most marked in young people and is seen throughout the UK, though there are substantial geographical variations in the incidence of some STIs. These changes suggest that the behavioural modifications adopted in response to the HIV/AIDS epidemic have not been sustained. Genital warts are the clinical manifestation of infection with certain types of human papillomavirus (HPV, particularly 6 and 11) and are the most common viral STI diagnosed in GUM clinics in England, Wales and Northern Ireland. In 2003, 70,665 first episodes of genital warts were diagnosed, a 2% increase since 2002 and a 27% increase since 1995. Genital warts continue to be concentrated in young people. The highest incidence is in London and the North West.4 Numbers of cases of genital warts represent only a fraction of the total pool of HPV infection. Infection with other HPV types, particularly 16, 18, 31 and 45, may lead to development of invasive cervical cancer and other cancers of the anogenital tract.9 Genital herpes is the most common ulcerative STI in England, Wales and Northern Ireland; almost 18,000 first episodes were diagnosed in 2003.4 For the first time since 1998, the incidence of diagnosed genital herpes declined, by 3% from 2002 to 2003; however, it is too soon to determine whether this marks an

Catherine M Lowndes is Head of the STI Section in the Department of HIV and Sexually Transmitted Infections at the Communicable Disease Surveillance Centre, Health Protection Agency Centre for Infections, London, UK. Conflicts of interest: none declared. Kevin A Fenton is Consultant Epidemiologist in HIV and Sexually Transmitted Infections at the Communicable Disease Surveillance Centre, Health Protection Agency Centre for Infections, London, UK. Conflicts of interest: none declared.

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ongoing downwards trend. Rates of diagnosis are largely uniform geographically; the highest incidence is seen in London (28% of all diagnoses). The incidence is greatest in women and men aged 20–24 years. In Scotland, there was a 39% increase (from 940 to 1310) in the number of laboratory reports of genital herpes infection from 2002 to 2003.10 Genital chlamydial infection is now the most commonly diagnosed STI in England, Wales and Northern Ireland. The prevalence ranges from 1% to 12% in studies of women attending general practice. The number of uncomplicated chlamydia diagnoses has increased sharply since the mid-1990s, to almost 90,000 in 2003 (Figure 3), an 8% increase since 2002 and a 190% increase since 1995.4 Numbers of diagnoses have increased across the UK; the greatest increases occurred in London and the North West. The incidence is highest in women aged 16–19 years (1334/100,000 in 2003) and in men aged 20–24 years (961/100,000), and the greatest increases have been in these groups. Greater public and professional awareness of this infection and developments in diagnostic test sensitivity have almost certainly

contributed to the increase in diagnoses, but substantial numbers of infections remain undiagnosed; about 70% of infections in women are thought to be asymptomatic. In England, phased implementation of the Department of Health’s National Chlamydia Screening Programme began in September 2002, targeting sexually active men and women under 25 years of age who attend a range of primary and community-based health-care facilities.11,12 In Scotland, laboratory diagnoses of genital chlamydia continued to increase. There were 14,407 reports during 2003 – a 16% increase since 2002 and an 88% increase since 2000.10 Gonorrhoea – some of the most dramatic changes in the incidence of STIs during the 1990s involved gonococcal infection.13,4 Between 1996 and 2002, the number of diagnoses of gonorrhoea increased by 106% to 24,958 in England, Wales and Northern Ireland. A small decrease of 4% (to 24,157) in numbers of reported cases occurred in 2003 relative to 2002 (Figure 1). The incidence of infection is highest in 16–19-year-old women (216/100,000 population in 2003) and 20–24-year-old men (291/100,000). Relatively large increases in the number of cases in young females suggest that heterosexually acquired infections

Diagnoses of gonorrhoea in GUM clinics in England and Wales, 1925–2003 Male Female Total

60000

Number of diagnoses

50000 40000 30000 20000 10000

0 1925 1931 1937 1943 1949 1955 1961 1967 1973 1979 1985 1991 1997 2003

12000

6000

10000

5000

8000

4000

6000

3000

4000

2000

2000

1000

Number of diagnoses (Scotland)

Number of diagnoses (England and Wales)

Diagnoses of syphilis (primary, secondary and early latent) in GUM clinics in England, Wales and Scotland, 1931–2003

0 0 1931 1943 1955 1967 1979 1991 2003 1937 1949 1961 1973 1985 1997

England and Wales, male England and Wales, female

Scotland, male Scotland, female

Source: KC60 statutory returns and ISD(D)5 data

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EPIDEMIOLOGY AND SEXUAL BEHAVIOUR

Diagnoses of uncomplicated genital chlamydial infection in the UK, 1994–2003

1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0

Diagnoses per 100,000

1995

1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0

1996

Diagnoses per 100,000

Men

1997

1998

1999

2000

2001

2002

1996

1997

1998

Gonorrhoea, 16–19 years Chlamydia, 16–19 years Genital warts, 16–19 years Genital herpes, 16–19 years

1999

2000

2001

2002

Men

1994

Women

1995

1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0

2003

Diagnoses per 100,000

Diagnoses per 100,000

Diagnoses of selected acute STIs in the UK, 1995–2003

1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0

1995

< 16 years 25–34 years

Gonorrhoea, 20–24 years Chlamydia, 20–24 years Genital warts, 20–24 years Genital herpes, 20–24 years

1996

1997

1998

1999

2000

2001

2002

2003

1997

1998

1999

2000

2001

2002

2003

Women

1994

2003

1995

1996

16–19 years 35–44 years

20–24 years ≥ 45 years

1995 data not available for Northern Ireland 2001–2003 data not available for Scotland

2001–2003 data not available for Scotland

Source: KC60 statutory returns and ISD(D)5 data

Source: KC60 statutory returns and ISD(D)5 data

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have increased significantly. Nevertheless, infections acquired through sex between men continue to account for a disproportionate number of infections. In 2003, 22% of cases of gonorrhoea in men were homosexually acquired, of which 49% were diagnosed in London. Several studies have also shown a disproportionate burden of gonorrhoea in urban black communities in the UK. This, in addition to the greater proportion of infection in men who have sex with men, partly explains why the incidence of gonorrhoea is higher in London than elsewhere. In Scotland, there were 825 laboratory reports of gonorrhoea in 2003, 81% of which were in men. An increase of 57% in numbers of reports occurred between 1999 and 2000; since then, there has been a 11% increase and a 37% decrease in numbers of reports from men and women respectively.10 Syphilis – relative to the other STIs, the incidence of syphilis is low.7,4 However, since 1999, substantial increases in numbers of syphilis diagnoses have been seen in men who have sex with men (1412%) and heterosexual males (468%) in England, Wales and Northern Ireland (Figure 1); 1399 cases were reported in

men in 2003. Men who have sex with men accounted for 56% of all cases seen in men in 2003. Diagnoses in women rose less dramatically between 1999 and 2003, by 229% to 181 cases. Unlike other bacterial STIs, the incidence of syphilis is greater in older age groups. Of heterosexual cases, 21% were acquired overseas in 2003.4 The increase in syphilis diagnoses has been associated with localized outbreaks in men who have sex with men (many of whom were also infected with HIV) in Brighton, Manchester, London, Newcastle upon Tyne and Central Scotland, and in heterosexuals in Bristol and London. 

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REFERENCES 1 Department of Health. The national strategy for sexual health and HIV implementation action plan. London: Department of Health, 2002. 2 Adler M W. The terrible peril: a historical perspective on the venereal diseases. BMJ 1980; 281: 206–11.

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3 Oriel J. The scars of venus. A history of venerology. Berlin: Springer-Verlag, 1994. 4 UK Collaborative Group for HIV and STI Surveillance. Focus on prevention. HIV and other sexually transmitted infections in the United Kingdom in 2003. London: Health Protection Agency Centre for Infections, 2004. 5 Righarts A A, Simms I, Wallace L et al. Syphilis surveillance and epidemiology in the United Kingdom. Eur Surveill 2004; 9: 15–16. 6 Gonococcal Resistance to Antimicrobials Surveillance Programme. Year 2003 collection. www.hpa.org.uk/infections/topics_az/hiv_ and_sti/sti-gonorrhoea/epidemiology/grasp.htm 7 Communicable Disease Surveillance Centre. Sexually transmitted diseases quarterly report: syphilis – national and international epidemiology. Commun Dis Rep CDR Wkly 1999; 9: 38–9. 8 Weller I, Hindley D, Adler M et al. Gonorrhoea in homosexual men and media coverage of the acquired immune deficiency syndrome in London 1982–3. BMJ 1984; 289: 1041. 9 Bosch F, Manos M, Nuñoz N et al. Prevalence of human papillomavirus in cervical cancer: a worldwide perspective. J Natl Cancer Inst 1995; 87: 796–802. 10 Wallace L A, Young H, Codere G et al. Genital herpes simplex, genital chlamydia and gonorrhoea infection in Scotland: laboratory diagnoses 1993–2003. Erratum. SCIEH Wkly Rep 2004; 38: 110–15. www.show.scot.nhs.uk/scieh 11 Department of Health. Main report of the Chief Medical Officer’s Expert Advisory Group on Chlamydia trachomatis. London: Department of Health, 1998. 12 Department of Health. National Chlamydia screening programme in England – programme overview, core requirements and data collection. 2nd ed. London: Department of Health, 2004. 13 Hughes G, Andrews N, Catchpole M et al. Investigation of the increased incidence of gonorrhoea diagnosed in genitourinary medicine clinics in England, 1994–6. Sex Transm Infect 2000; 76: 18–24.

Practice points • Diagnoses of acute STIs in the UK have increased considerably during the last 5 years, particularly in teenagers • It is likely that behavioural modifications adopted in response to the HIV/AIDS epidemic have not been sustained • Disease surveillance has an important role in monitoring disease trends, understanding the determinants of STI transmission and informing disease prevention efforts • Delivery of effective STI prevention interventions is a key public health imperative; however, these must be appropriate and relevant to those at greatest risk, particularly young, sexually active individuals

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