The role of epidemiology and surveillance systems in the control of sexually transmitted diseases

Recorded gonorrhoea rates in Denmark, 1900-2010: the impact of clinical testing activity and laboratory diagnostic procedures

OBJECTIVES

Assessment of the relations between recorded gonorrhoea rates and clinical testing activity and disposable diagnostic tests.

METHODS

In Denmark, two sources of information on the epidemiology of gonorrhoea are available: (1) a mandatory clinical notification system (since 1867) comprising summary information about geographic distribution, season, age group and gender; in 1994, more detailed anonymous individualised epidemiological information was included; (2) a voluntary countrywide laboratory surveillance system for culture-confirmed cases (since 1957) comprising information about patient's age and gender, infected anatomical sites and medical setting attended.

RESULTS

Both surveillance systems showed marked simultaneous changes in gonorrhoea rates, although periodically considerable under-reporting or under-diagnosing was demonstrated. The annual incidence of notified cases peaked in 1919 (474/100,000), in 1944 (583/100,000) and in 1972 (344/100,000). Since 1995, the incidence has been at a low endemic level (1.5-10/100,000) and the total male/female incidence ratios were from 3 to 7 times higher than previously recorded. Among approximately 2 million persons tested during 1974-1988 78,213 men and 63,143 women with culture-confirmed gonorrhoea were identified. During this period, pharyngeal sampling was performed in 36% of men and 25% of women with gonorrhoea; pharyngeal gonorrhoea was found in 10% and 16%, respectively; 40% and 30% of these patients had no concomitant urogenital gonorrhoea. Among men with gonorrhoea, 34% were sampled from the rectum; 9% had rectal gonorrhoea, among whom the rectum was the only infected site in 67%.

CONCLUSIONS

Crucial factors for case finding are clinical sampling tradition and appropriate laboratory diagnostic facilities. When case finding is insufficient, a reservoir of asymptomatic rectal or pharyngeal gonorrhoea remains unrecognised.

The emerging HIV epidemic on the Mexico-U.S. border: an international case study characterizing the role of epidemiology in surveillance and response

PURPOSE

Human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome surveillance data are critical for monitoring epidemic trends, but they can mask dynamic subepidemics, especially in vulnerable populations that underuse HIV testing. In this case study, we describe community-based epidemiologic data among injection drug users (IDUs) and female sex workers (FSWs) in two northern Mexico-U.S. border states that identified an emerging HIV epidemic and generated a policy response.

METHODS

We draw from quantitative and qualitative cross-sectional and prospective epidemiologic studies and behavioral intervention studies among IDUs and FSWs in Tijuana, Baja California, and Ciudad Juarez, Chihuahua.

RESULTS

The recognition that the HIV epidemic on Mexico's northern border was already well established in subgroups in whom it had been presumed to be insignificant was met with calls for action and enhanced prevention efforts from researchers, nongovernmental organizations, and policy makers.

CONCLUSIONS

Successful policies and program outcomes included expansion of needle-exchange programs, a nationwide mobile HIV prevention program targeting marginalized populations, a successful funding bid from the Global Fund for HIV, TB, and Malaria to scale up targeted HIV-prevention programs, and the establishment of bi-national training programs on prevention of HIV and substance use. We discuss how epidemiologic data informed HIV prevention policies and suggest how other countries may learn from Mexico's experience.

The characteristics of sexual behavior and extent of condom usage among sexually active Croatians from Eastern Croatia

OBJECTIVE

To determine the extent of condom usage as a method of protection from sexually transmitted infections (STIs) among sexually active individuals obliged to present for periodical health examination at the Institute of Public Health for the Osijek-Baranya County, in Osijek, eastern Croatia.

MATERIAL AND METHODS

During February 2004, a cross-sectional questionnaire survey was conducted. The research tool was an unidentified 20-item questionnaire addressing the sexual behavior of study subjects and their partners and methods of protection from STIs. Descriptive statistics and χ(2) - test were used for data analysis.

RESULTS

The response rate was 84.2% (278/330). A total of 278 subjects, 96 (34.5%) males and 182 (65.5%) females, 167 (60.1%) married and 111 (39.9%) single, mean age 31.3±8.4, age range 18-52 years were enrolled in the study. Study results revealed 22.3% (62/278) subjects to have had two or more sexual partners over the one-year period and the use of condom was reported by 40.3% (25/62) of those subjects.

CONCLUSIONS

The obtained results point to the need for additional education on protection from sexually transmitted infections and on risky sexual behavior, with special reference to the role of condom usage in the prevention of these diseases and their detrimental effects on the reproductive health of sexually active individuals.

Collecting data for sexually transmitted infections (STI) surveillance: what do patients prefer in Flanders?

Background

STI surveillance systems are subject to qualitative and quantitative underreporting. General practitioners (GPs), who are key subjects in case reporting, explain their underreporting partly by their observation that taking a sexual history is embarrassing for patients, and that patients are reluctant to disclose information on their sexual practices. In this study we examine patients' willingness to provide data for STI surveillance.

Methods

A questionnaire-based survey in a stratified population sample of 300 patients aged 18–60 years.

Results

The large majority of respondents stated to be willing to give information on their sexual practices for the purpose of STI surveillance. They preferred to answer sexual history questions to their GP; filling in a form on the internet was the second best option.

Conclusion

Based on these results, it is unlikely that the cooperation of patients would be a weak link in STI surveillance strategies. This observation, together with the fact that the majority of patients at risk for STIs have regular access to general practice services, justify renewed efforts to enliven primary care-based STI surveillance strategies.

What can be gained from comprehensive disaggregate surveillance? The Avon Surveillance System for Sexually Transmitted Infections

OBJECTIVE

To describe a new disaggregate surveillance system covering key diagnosed sexually transmitted infections in a UK locality.

METHODS

The Avon System for Surveillance of Sexually Transmitted Infections (ASSIST) collects computerised person- and episode-based information about laboratory-diagnosed sexually transmitted infections from genitourinary medicine (GUM) clinics, the Avon Brook Clinic, and the Health Protection Agency and trust laboratories in primary care trusts in Avon. The features of the system are illustrated here, by describing chlamydia-testing patterns according to the source of test, age and sex, and by mapping the distribution of chlamydia across Bristol, UK.

RESULTS

Between 2000 and 2004, there were 821,685 records of tests for sexually transmitted infections, with 23,542 positive results. The proportion of tests and positive results for chlamydia and gonorrhoea sent from general practice increased over time. Most chlamydia tests in both GUM and non-specialist settings were performed on women aged >25 years, but positivity rates were highest in women aged <25 years. The positivity rate remained stable between 2000 and 2004. Including data from all diagnostic settings, chlamydia rates were about twice as high as those estimated only from genitourinary clinic cases.

CONCLUSIONS

The ASSIST model could be a promising new tool for planning and measuring sexual health services in England if it can become sustainable and provide more timely data using fewer resources. Collecting denominator data and including infections diagnosed in primary care are essential for meaningful surveillance.

Surveillance systems for STIs in the European Union: facing a changing epidemiology

OBJECTIVES

To characterise the nature, content, and performance characteristics of existing national STI surveillance systems in the European Union (EU) and Norway, to facilitate collection of comparable surveillance data.

METHODS

Cross sectional survey using a structured questionnaire.

RESULTS

Case reporting from clinicians and/or laboratories is the mainstay of EU surveillance systems for bacterial STIs. Coverage of case reporting varies from less than 10% to over 75%, and lack of and/or heterogeneity in case definitions affect the relative specificity and sensitivity of reporting systems. Considerable variations also exist in STI care sites; the populations who use these services; and in partner notification practices, STI screening practices, and STI laboratory diagnostic tests employed, affecting the representativeness of reported data and the sensitivity of surveillance systems for detecting the true number of STI cases.

CONCLUSIONS

The heterogeneity of current surveillance systems complicates direct comparison of STI incidence rates across Europe. Introduction of standardised case definitions for reporting, and increased coverage of mandatory reporting systems where necessary, are needed. Definition of standardised minimum datasets and use of sentinel and enhanced surveillance systems to supplement universal case/laboratory notification data, could improve our understanding of the distribution and determinants of STIs across Europe, and aid in the design of effective public health responses. In the context of the changing epidemiology of STIs, systems for detection and monitoring of localised outbreaks of acute bacterial STIs (syphilis and antimicrobial resistant gonorrhoea), as well as prevalence monitoring systems for frequently asymptomatic STIs (chlamydial infection and viral STIs), are also necessary.

Assessing the impact of national anti-HIV sexual health campaigns: trends in the transmission of HIV and other sexually transmitted infections in England

OBJECTIVE

To assess the impact of the sexual component of AIDS and HIV campaigns on transmission of HIV and other sexually transmitted infections (STIs).

DESIGN

Comparison of time series data.

SETTING

England, 1971-1999.

OUTCOME MEASURES

HIV transmission and diagnoses among men who have sex with men (MSMs), rates of attendances and specific STI diagnoses (per 100 000 total population) at genitourinary medicine (GUM) clinics.

RESULTS

Awareness of AIDS and campaigns in 1983-4 among homosexual men coincided with substantial declines in transmission of HIV and diagnoses of syphilis among MSMs. During general population campaigns in 1986-7 new GUM clinic attendances requiring treatment fell by 117/10(5) in men and 42/10(5) in women. Rates for gonorrhoea fell by 81/10(5) and 43/10(5) and genital herpes by 6/10(5) and 4/10(5), respectively. Previous rises in genital wart rates were interrupted, while rates of attendances not requiring treatment (the "worried well") increased by 47/10(5) and 58/10(5) for men and women, respectively. Since 1987 diagnoses of HIV among MSMs have not declined, averaging 1300-1400 annually. Following a period of unchanging rates there have been substantial increases in GUM attendances requiring treatment, notably for gonorrhoea, syphilis, and viral STIs since 1995.

CONCLUSIONS

Self help initiatives and awareness among homosexual men in 1983-4 contributed significantly to a fall in HIV transmission among MSMs, and the general campaigns of 1986-7 were associated with similar effects on all STI transmission. Both effects seem to have occurred through changing sexual behaviour, and probably contributed to the UK's low national HIV prevalence. Bacterial STI incidence has increased significantly since 1995 and there is no evidence that recent prevention initiatives have reduced HIV transmission among MSMs, hence sexual health initiatives need to be comprehensively reinvigorated in England.

The control of syphilis, a contemporary problem: a historical perspective

The control of syphilis in the United Kingdom and United States has been managed in different ways in each country over the course of the last century. Older more established measures including contact tracing, serological surveillance, and health education strategies together with effective antibiotic therapy have had some success. However, changing social structures on both sides of the Atlantic Ocean have brought newer mathematical and epidemiological methods to the fore. This review looks at the past management of syphilis control in the United Kingdom and United States, and speculates on future prospects for disease management in these countries.

The transmission dynamics of gonorrhoea: modelling the reported behaviour of infected patients from Newark, New Jersey

A survey of the sexual behaviour of gonorrhoea patients in Newark was undertaken to evaluate parameters within a model of gonorrhoea transmission. Modelling work aimed to explain observed epidemiological patterns and to explore the potential impact of interventions. Reported behaviours, along with values derived from the literature, were used within a standard deterministic model of gonorrhoea transmission, where the population was stratified according to sex and rates of sex-partner change. The behaviours reported, particularly among women, are insufficient by themselves to explain the continued existence of gonorrhoea within the population. The majority of symptomatic patients seek treatment within a few days, and report that they do not have unprotected sex while symptomatic. The proportion of patients with low numbers of sex partners suggests that sexual mixing between people categorized according to sexual behaviour is near random. To explain the persistence of gonorrhoea, there must be some patients who, when infected, do not seek care in public clinics. In addition, gonorrhoea incidence in the model is sensitive to change, such that very small reductions in risk behaviour could lead to its elimination. This does not accord with the observed failure of many interventions to eliminate infection, suggesting that the modelled infection is too sensitive to change. The model, which has been influential in gonorrhoea epidemiology, is not consistent with the observed epidemiology of gonorrhoea in populations. Alternative models need to explore the observed stability of gonorrhoea before robust modelling conclusions can be drawn on how best to control infection. However, the current results do highlight the potential importance of asymptomatic infections and infections in those who are diseased and do not attend public health services. Screening and contact-tracing to identify asymptomatic infections in both men and women will be more effective in reaching those who maintain the infection within the community rather than simply treating symptomatic cases.

Susceptibility of gonococci isolated in London to therapeutic antibiotics: establishment of a London surveillance programme. London Gonococcal Working Group

OBJECTIVES

To establish the in vitro susceptibility of gonococci isolated in the London area to antibiotics in current therapeutic use and to establish a sentinel surveillance system for monitoring trends in antibiotic resistant gonorrhoea in London.

METHODS

Isolates of Neisseria gonorrhoeae from consecutive patients attending genitourinary medicine clinics at 10 hospitals in the London area were collected over a 3 month period, May to July 1997. The susceptibility to penicillin, ciprofloxacin, tetracycline, and spectinomycin was determined for each isolate. Isolates exhibiting either plasmid or chromosomally mediated resistance were additionally tested for susceptibility to agents used as alternative treatments including azithromycin, ceftriazone, and ofloxacin. The resistant isolates were also tested for plasmid profiles (penicillinase producing N gonorrhoeae, PPNG), type of tetM determinant (tetracycline resistant N gonorrhoeae, TRNG), and presence of gyrA and parC mutations (quinolone resistant N gonorrhoeae, QRNG).

RESULTS

A total of 1133 isolates were collected which represents > 95% of the total gonococci isolated in the 3 months. Plasmid mediated resistance was exhibited by 48 (4.2%) isolates; six (0.5%) were PPNG, 15 (1.3%) were PP/TRNG, and 27 (2.4%) were TRNG. The majority of PPNG (18 of 20 tested) carried the 3.2 MDa penicillinase plasmid whereas the two types of tetM determinant were more evenly distributed. High level resistance to ciprofloxacin was detected in four (0.4%) isolates and double mutations were found in the quinolone resistance determining region (QRDR) of the gyrA gene in three QRNG with MICs of 16 mg/l and a single mutation in one isolate with a MIC of 1 mg/l to ciprofloxacin. No parC mutations were found. Of the remaining 1081 isolates, 86 (8.0%) were chromosomally mediated resistant N gonorrhoeae (CMRNG).

CONCLUSIONS

A unique collection of gonococcal isolates has been established which can be used as a baseline for surveillance of susceptibility to antibiotics and for epidemiological purposes.