Geographic epidemiology of gonorrhoea and chlamydia on a large military installation: application of a GIS system

Incorporating Geographic Information Science and Technology in Response to the COVID-19 Pandemic

Incorporating geographic information science and technology (GIS&T) into COVID-19 pandemic surveillance, modeling, and response enhances understanding and control of the disease. Applications of GIS&T include 1) developing spatial data infrastructures for surveillance and data sharing, 2) incorporating mobility data in infectious disease forecasting, 3) using geospatial technologies for digital contact tracing, 4) integrating geographic data in COVID-19 modeling, 5) investigating geographic social vulnerabilities and health disparities, and 6) communicating the status of the disease or status of facilities for return-to-normal operations. Locations and availability of personal protective equipment, ventilators, hospital beds, and other items can be optimized with the use of GIS&T. Challenges include protection of individual privacy and civil liberties and closer collaboration among the fields of geography, medicine, public health, and public policy.

Modelling individual vulnerability to sexually transmitted infections to optimise intervention strategies: analysis of surveillance data from Kalamazoo County, Michigan, USA

OBJECTIVE

We modelled individual vulnerability to STI using personal history of infection and neighbourhood characteristics.

METHODS

Retrospective chlamydia and gonorrhoea data of reported confirmed cases from Kalamazoo County, Michigan for 2012 through 2014 were analysed. Unique IDs were generated from the surveillance data in collaboration with local health officials to track the individual STI histories. We then examine the concept that individuals with similar STI histories form a 'peer' group. These peer group include: (1) individuals with a single chlamydia; (2) individuals with single gonorrhoea; (3) individuals with repeated cases of one type of STI and (4) individuals that were diagnosed with both infections during the study period. Using Kernel density estimation, we generated densities for each peer group and assigned the intensity of the infection to the location of the individual. Finally, the individual vulnerability was characterised through ordinary least square regression (OLS) using demographics and socioeconomic variables.

RESULTS

In an OLS regression adjusted for frequency of infection, individual vulnerability to STI was only consistently significant for race and neighbourhood-level socioeconomic status (SES) in all the models under consideration. In addition, we identified six areas in three townships in Kalamazoo County that could be considered for unique interventions based on overlap patterns among peer groups.

CONCLUSIONS

The results provide evidence that individual vulnerability to STI has some dependency on individual contextual (race) and exogenous factors at the neighbourhood level such as SES, regardless of that individual's personal history of infection. We suggest place-based intervention strategies be adopted for planning STI interventions instead of current universal screening of at-risk populations.

The Association between Sexually Transmitted Infections, Length of Service and Other Demographic Factors in the U.S. Military

BACKGROUND

Numerous studies have found higher rates of sexually transmitted infections (STIs) among military personnel than the general population, but the cumulative risk of acquiring STIs throughout an individual's military career has not been described.

METHODS

Using ICD-9 diagnosis codes, we analyzed the medical records of 100,005 individuals from all service branches, divided in equal cohorts (n = 6,667) between 1997 and 2011. As women receive frequent STI screening compared to men, these groups were analyzed separately. Incidence rates were calculated for pathogen-specific STIs along with syndromic diagnoses. Descriptive statistics were used to characterize the individuals within each accession year cohort; repeat infections were censored.

RESULTS

The total sample included 29,010 females and 70,995 males. The STI incidence rates (per 100 person-years) for women and men, respectively, were as follows: chlamydia (3.5 and 0.7), gonorrhea (1.1 and 0.4), HIV (0.04 and 0.07) and syphilis (0.14 and 0.15). During the study period, 22% of women and 3.3% of men received a pathogen-specific STI diagnosis; inclusion of syndromic diagnoses increased STI prevalence to 41% and 5.5%, respectively. In multivariate analyses, factors associated with etiologic and syndromic STIs among women included African American race, younger age and fewer years of education. In the overall sample, increasing number of years of service was associated with an increased likelihood of an STI diagnosis (p<0.001 for trend).

CONCLUSION

In this survey of military personnel, we found very high rates of STI acquisition throughout military service, especially among women, demonstrating that STI-related risk is significant and ongoing throughout military service. Lower STI incidence rates among men may represent under-diagnosis and demonstrate a need for enhancing male-directed screening and diagnostic interventions.

All Military Adolescents Are Not the Same: Sexuality and Substance Use among Adolescents in the U.S. Military Healthcare System

Data examining sexuality and substance use among active duty and military-dependent youth is limited; however, these psychosocial factors have military implications. Adolescents and young adults aged 12–23 were recruited from an active-duty trainee clinic (n = 225) and a military pediatric clinic (n = 223). Active duty participants were more likely to be older, male, White, previous tobacco users, and report a history of sexual activity and less contraception use at their most recent intercourse, compared to the dependent group. Over 10% of all participants indicated attraction to members of the same gender or both genders. In logistic regression analysis, non-White participants were less likely to use contraception compared to White participants. Adolescents and young adults seen in military clinics frequently engage in high-risk behavior. Clinicians who care for military youth should assess their patient’s psychosocial history. Further study of this population is warranted to identify factors that may influence risk and resilience.

Chlamydia trachomatis infection rates among a cohort of mobile soldiers stationed at Fort Bragg, North Carolina, 2005-2010

Background

Fort Bragg, a large Army installation with reported high Chlamydia trachomatis (Ct) infection rates, is characterized by a highly mobile population and a surrounding Ct-endemic community. We assessed the rates of Ct incidence and recurrence among the installation’s active component Army personnel and determined the association of soldier transience, sociodemographic factors, and history of sexually transmitted infection (STI) with these rates.

Methods

A cohort of soldiers stationed at Fort Bragg during 2005 to mid-2010 was followed for incident and recurrent Ct infection using laboratory-confirmed reportable disease data. Linkage to demographic and administrative data permitted multivariate analysis to determine association of covariates with initial or recurrent infection.

Results

Among 67,425 soldiers, 2,198 (3.3%) contracted an incident Ct infection (crude incidence, 21.7 per 1,000 person-years). Among soldiers followed for incident infection, 223 (10.6%, crude incidence 110.8 per 1,000 person-years) contracted a recurrent Ct infection. Being female, of lower rank, under 26 years of age, of non-white race, single, or with a high school diploma or less was significantly associated with incident Ct infection. Having breaks in duty or having deployments during follow-up was associated with a lower infection rate. Among women, having prior deployments was associated with a lower rate of both incident and recurrent infection. Specifically associated with recurrent infection in women was age under 21 years or no education beyond high school.

Conclusions

This analysis reaffirms risk factors for Ct infection determined in other studies. In addition, infection risk was lower for more mobile soldiers and tied to the specific location of their regular duty assignment. The findings support the STI prevention efforts at Fort Bragg and the surrounding community, regardless of how often or for how long soldiers have deployed for military operations.

Sexual behaviors and sexually transmitted infections in a nationally representative sample of women veterans and nonveterans

BACKGROUND

Women veterans are a growing population with unique characteristics and documented health disparities. Few studies have examined their sexual behaviors and rates of sexually transmitted infections (STIs), and none have compared women veterans to nonveterans to identify potential sexual health disparities.

METHODS

We used data from the 1999-2010 National Health and Nutrition Examination Survey, a nationally representative U.S. survey. We compared lifetime sexual history (age at first intercourse, number of partners), sexual activity in the last year, and STIs between women veterans (n=151) and nonveterans (n=8738), adjusting for age, race/ethnicity, education, marital status, binge drinking, and survey year.

RESULTS

Compared to nonveterans, women veterans reported a younger age at first intercourse and a greater number of female and male lifetime sexual partners, and they were more likely to have ever had sex with a woman. They were also more likely than nonveterans to have genital herpes and genital warts.

CONCLUSIONS

Women veterans reported higher rates of sexual activity and STIs than nonveterans. Future research is needed to assess high-risk behaviors and determine what factors may underlie these associations. Providers should ensure thorough screening and intervention services are provided for this growing population.

Prevalence and factors associated with asymptomatic gonococcal and chlamydial infection among US Navy and Marine Corps men infected with the HIV: a cohort study

OBJECTIVES

Neisseria gonorrhoeae (GC) and Chlamydia trachomatis (CT) can facilitate transmission of HIV. Men who have sex with men (MSM) may harbour infections at genital and extragenital sites. Data regarding extragenital GC and CT infections in military populations are lacking. We examined the prevalence and factors associated with asymptomatic GC and CT infection among this category of HIV-infected military personnel.

DESIGN

Cross-sectional cohort study (pilot).

SETTING

Infectious diseases clinic at a single military treatment facility in San Diego, CA.

PARTICIPANTS

Ninety-nine HIV-positive men were evaluated-79% men who had sex with men, mean age 31 years, 36% black and 33% married.

INCLUSION CRITERIA

male, HIV-infected, Department of Defense beneficiary.

EXCLUSION CRITERIA

any symptom related to the urethra, pharynx or rectum.

PRIMARY OUTCOME MEASURES

GC and CT screening results.

RESULTS

Twenty-four per cent were infected with either GC or CT. Rectal swabs were positive in 18% for CT and 3% for GC; pharynx swabs were positive in 8% for GC and 2% for CT. Only one infection was detected in the urine (GC). Anal sex (p=0.04), male partner (OR 7.02, p=0.04) and sex at least once weekly (OR 3.28, p=0.04) were associated with infection. Associated demographics included age <35 years (OR 6.27, p=0.02), non-Caucasian ethnicity (p=0.03), <3 years since HIV diagnosis (OR 2.75, p=0.04) and previous sexually transmitted infection (STI) (OR 5.10, p=0.001).

CONCLUSIONS

We found a high prevalence of extragenital GC/CT infection among HIV-infected military men. Only one infection was detected in the urine, signalling the need for aggressive three-site screening of MSM. Clinicians should be aware of the high prevalence in order to enhance health through comprehensive STI screening practices.

High-risk behavior and sexually transmitted infections among U.S. active duty servicewomen and veterans

The number of women who are active duty service members or veterans of the U.S. military is increasing. Studies among young, unmarried, active duty servicewomen who are sexually active indicate a high prevalence of risky sexual behaviors, including inconsistent condom use, multiple sexual partners, and binge drinking, that lead to unintended and unsafe sex. These high-risk sexual practices likely contribute to chlamydia infection rates that are higher than the rates in the U.S. general population. Human papillomavirus (HPV) infection and cervical dysplasia may also be higher among young, active duty servicewomen. Little is known about the sexual practices and rates of sexually transmitted infections among older servicewomen and women veterans; however, women veterans with a history of sexual assault may be at high risk for HPV infection and cervical dysplasia. To address the reproductive health needs of military women, investigations into the prevalence of unsafe sexual behaviors and consequent infection among older servicewomen and women veterans are needed. Direct comparison of military and civilian women is needed to determine if servicewomen are a truly high-risk group. Additionally, subgroups of military women at greatest risk for these adverse reproductive health outcomes need to be identified.

What do we need to learn for policy decision-making on sexually transmitted infections prevention and treatment in Israel?

The rising trend of sexually transmitted infections (STIs) reported in several western countries has also affected Israel. To review epidemiological trends and to address additional issues needed for a wider overview on STIs in Israel, we analysed notified data on infectious syphilis, gonorrhoea, Chlamydia trachomatis and HIV/AIDS during 1998–2007, by age groups, and each available publication on STIs in Israel. The trend of each disease had a unique pattern, probably influenced by different screening procedures, case definition, mix of populations and better access to care for high-risk populations. Higher rates were found among patients aged 25–34 years. Rates found in different peak years for gonorrhoea, HIV, chlamydia and infectious syphilis reached 43.6, 18.9, 10.8 and 8.1 cases per 100,000 population, respectively. We compare trends to those of countries from World Health Organization (WHO) European Region and discuss interventions for subpopulations on which additional data are needed for evidence-based policy-making. Incidence rates of syphilis, gonorrhoea, chlamydia and HIV/AIDS are still low in Israel. We propose additional components needed for a more comprehensive evidence-based policy on STIs.

Spatial visualization of multivariate datasets: an analysis of STD and HIV/AIDS diagnosis rates and socioeconomic context using ring maps

OBJECTIVES

We used existing data systems to examine sexually transmitted disease (STD) and HIV/AIDS diagnosis rates and explore potential county-level associations between HIV/AIDS diagnosis rates and socioeconomic disadvantage.

METHODS

Using South Carolina county data, we constructed multivariate ring maps to spatially visualize syphilis, gonorrhea, chlamydia, and HIV/AIDS diagnosis rates; gender- and race-specific HIV/AIDS diagnosis rates; and three measures of socioeconomic disadvantage-an unemployment index, a poverty index, and the Townsend index of social deprivation. Statistical analyses were performed to quantitatively assess potential county-level associations between HIV/AIDS diagnosis rates and each of the three indexes of socioeconomic disadvantage.

RESULTS

Ring maps revealed substantial spatial association in STD and HIV/AIDS diagnosis rates and highlighted large gender and racial disparities in HIV/AIDS across the state. The mean county-level HIV/AIDS diagnosis rate (per 100,000 population) was 24.2 for males vs. 11.2 for females, and 34.8 for African Americans vs. 5.2 for white people. In addition, ring map visualization suggested a county-level association between HIV/AIDS diagnosis rates and socioeconomic disadvantage. Significant positive bivariate relationships were found between HIV/AIDS rate categories and each increase in poverty index category (odds ratio [OR] = 2.03; p=0.006), as well as each increase in Townsend index of social deprivation category (OR=4.98; p<0.001). A multivariate ordered logistic regression model in which all three socioeconomic disadvantage indexes were included showed a significant positive association between HIV/AIDS and Townsend index categories (adjusted OR=6.10; p<0.001).

CONCLUSIONS

Ring maps graphically depicted the spatial coincidence of STD and HIV/AIDS and revealed large gender and racial disparities in HIV/AIDS across South Carolina counties. This spatial visualization method used existing data systems to highlight the importance of social determinants of health in program planning and decision-making processes.

Detection of Babesia vogeli in stray cats of metropolitan Bangkok, Thailand

The combination of a rapidly growing stray animal population and the lack of animal control in Bangkok has resulted in a unique opportunity to evaluate the potential role of companion animals as sentinels and reservoirs of infectious diseases, including several of those caused by vector-borne parasites. The purpose of this study was to determine the prevalence and factors associated with the distribution of Babesia species infections among stray cats in Bangkok. Blood samples were collected from 1490 stray cats residing in 140 monasteries of 50 metropolitan districts of Bangkok, and assayed with light microscopy and PCR for evidence of Babesia spp. Pear-shaped merozoites were observed microscopically from two (0.13%) of these cats, while a nested 18S rDNA-based PCR assay detected babesial infections in 21 (1.4%) of the cats tested. The prevalence of infection was significantly different between sexes (p<0.05), and PCR-positive cats were found in 30% (15/50) of the districts surveyed. All 21 amplicon sequences were identical, and were determined to be closest to that reported for B. vogeli (98% identity). These results represent the first molecular confirmation that a Babesia sp. is enzootic among stray cat populations in Thailand, and suggest that the presence of pet companion animals could be a risk factor for exposure of stray cats to vector-borne parasites.

Development and Evaluation of GIS-Based Chlamydia Trachomatis Intervention Policy in Illinois

Chlamydia trachomatis is the most prevalent infectious disease in the United States. Complications include pelvic inflammatory disease (PID), ectopic pregnancy, and infertility. The cost of PID in 1998 was estimated at greater than $1.9 billion. Screening intervention strategies are often consumed by those at low risk. The objective of this study is the development of a more cost-effective intervention strategy by employing Geographic Information Systems and Census Bureau demographic data in selected Local Health Departments in Illinois. Case studies of intervention activities at the state and local level were performed. An evaluability assessment model of current inputs, processes and outcomes was created. A proposed model utilizing additional state inputs was developed and tested. Interventions were evaluated for effectiveness in reducing the incidence of Chlamydia trachomatis. Societal cost effectiveness analysis was also performed. The proposed model was tested in 2006. Results indicate that only minimal changes in annual incidence are required for GIS-augmented interventions to be cost-effective.

USING PARTICIPATORY METHODS AND GEOGRAPHIC INFORMATION SYSTEMS (GIS) TO PREPARE FOR AN HIV COMMUNITY-BASED TRIAL IN VULINDLELA, SOUTH AFRICA (Project Accept-HPTN 043)

Recent attempts to integrate geographic information systems (GIS) and participatory techniques, have given rise to terminologies such as participatory GIS and community-integrated GIS. Although GIS was initially developed for physical geographic application, it can be used for the management and analysis of health and health care data. Geographic information systems, combined with participatory methodology, have facilitated the analysis of access to health facilities and disease risk in different populations. Little has been published about the usefulness of combining participatory methodologies and GIS technology in an effort to understand and inform community-based intervention studies, especially in the context of HIV. This article attempts to address this perceived gap in the literature. The authors describe the application of participatory research methods with GIS in the formative phase of a multisite community-based social mobilization trial, using voluntary counseling and testing and post-test support as the intervention.

Traditional sexually transmitted disease prevention and control strategies: tailoring for African American communities

African Americans carry the largest disease burden for bacterial sexually transmitted diseases (STDs) in the United States. These infections can have a devastating impact on sexual and reproductive health if they are not diagnosed and treated. Traditionally, public health efforts to prevent and control bacterial STDs have been through surveillance, clinical services, partner management, and behavioral intervention strategies. However, the persistence of disparities in STDs indicates that these strategies are not achieving sufficient impact in African American communities. It may be that factors such as limited access, acceptability, appropriateness, and affordability of services reduce the efficacy of these strategies for African American communities. In this article we describe the STD prevention strategies and highlight the challenges and implications of these strategies in addressing disparities in African American communities.

Spatial pattern of HIV-1 mother-to-child-transmission in Madrid (Spain) from 1980 till now: demographic and socioeconomic factors

OBJECTIVE

To evaluate any possible association between indicators of social inequalities and the geographical distribution of HIV-1 mother-to-child transmission (MTCT) cases in Madrid.

METHODS

We carried out an observational survey of 224 HIV-1 vertically infected children born in 1980-2006 living in Madrid. We elaborated maps representing the prevalence of HIV-1 MTCT cases. We assessed the association between indicators of social inequalities and the spatial distribution of MTCT cases. Poisson univariate and multivariate analysis of risk factors for MTCT were performed.

RESULTS

We identified core areas of transmission mainly in southern Madrid until 2006. The prevalence of MTCT cases was significantly correlated to the percentage of immigrants, illiterates, unemployed women and the income in 1996 and 2000/2001. The risk of MTCT increased in the periods up to 1996 compared with the calendar period 1980-1989, whereas the risk decreased in 1999-2006 [relative risk, 0.08; 95% confidence interval (CI), 0.03-0.18; P < 0.001]. The risk was especially high in the districts of Usera (absolute relative risk, 11.4; 95% CI, 2.6-49.5; P = 0.001), Puente de Vallecas (absolute relative risk, 14.0; 95% CI, 3.4-57.9; P < 0.001) and San Blas (absolute relative risk, 12.5; 95% CI, 2.9-53.6; P = 0.001). The percentage of illiterates was the indicator that explained the risk of MTCT (absolute relative risk, 1.07; 95% CI, 1.05-1.10; P = 0.001).

CONCLUSION

We observed a geographic heterogeneity of the HIV-1 vertical transmission with the highest prevalence in disadvantaged districts. What is described in the present review is the HIV-1 vertical transmission within a social context; this approach could be relevant in analysing the pattern of HIV-1 transmission in other Western cities or highlighting the distribution of other infectious diseases.

Spatial distribution of HIV prevalence and incidence among injection drugs users in St Petersburg: implications for HIV transmission

INTRODUCTION

The HIV/AIDS epidemic in St Petersburg, as in much of Russia, is concentrated among injection drug users (IDU) in whom prevalence reached 30% in 2003. Understanding the dynamics of the epidemic is important in developing appropriate responses in the resource-constrained context of Russian cities such as St Petersburg.

METHODS

IDU were contacted and screened to create a seronegative cohort for prevention and vaccine studies. At screening, individuals provided sociodemographic, drug use, and injection and sex-related risk behavior data. Seronegative individuals who enrolled in the cohort were followed for one year and tested for HIV semiannually. Residential addresses were entered into a geographical information system programme and analysed for spatial clustering using Moran's I and nearest-neighbor analysis.

RESULTS

We mapped 788 of the 900 study participants to discrete locations within St Petersburg; 236 (29.9%) were HIV seropositive at baseline. Although there was no clustering of the study population as a whole, HIV-infected individuals were tightly clustered and prevalence co-clustered with high frequency of heroin injection, receptive syringe sharing, being younger than 24 years, and living with parents. These clusters were restricted to 5% of populated areas of the city. We mapped 18 of 20 incident cases detected among the cohort, and more than half were located within or adjacent to the clusters.

INTERPRETATION

Spatial analysis identified linkages between disease prevalence and risky injection behaviors that were not evident using traditional epidemiological analysis. The analysis also identified where resources might be allocated geographically for maximum impact in slowing the HIV epidemic among IDU.

Use of geographic information systems for planning HIV prevention interventions for high-risk youths

Geographic information system (GIS) analysis is an emerging tool for public health intervention planning. Connect to Protect, a researcher-community collaboration working in 15 cities to reduce HIV infection among youths, developed GIS databases of local health, crime, and demographic data to evaluate the geographic epidemiology of sexually transmitted infections and HIV risk among adolescents. We describe the process and problems of data acquisition, analysis, and mapping in the development of structural interventions, demonstrating how program planners can use this technology to inform and improve planning decisions. The Connect to Protect project's experience suggests strategies for incorporating public data and GIS technology into the next generation of public health interventions.

Infections in confined spaces: cruise ships, military barracks, and college dormitories

The presence of a vast cohort of individuals in semi-confined settings such as cruise ships, military barracks, and college dormitories is often accompanied by an increase in the risk of particular infections. These are often gastrointestinal infections on cruise ships and respiratory pathogens that are easily transmitted in the barrack and dormitory setting. The control of these infections involves attention to good personal hygiene, safe food and water handling, and use of vaccines to prevent vaccine-preventable diseases.

Modeling a syphilis outbreak through space and time using the Bayesian maximum entropy approach

PURPOSE

The aim of the study is to describe changes in the spatial distribution of syphilis before, during, and after an outbreak in Baltimore, MD, by using Bayesian maximum entropy (BME), a modern geostatistical technique for space-time analysis and mapping.

METHODS

BME was used to conduct simple and composite space-time analyses of the density of syphilis infection based on primary, secondary and early latent syphilis cases reported to the Baltimore City Health Department between January 1, 1994, and December 31, 2002.

RESULTS

Spatiotemporal covariance plots indicated that the distribution of the density of syphilis cases showed both spatial and temporal dependence. Temporally dependent disease maps suggested that syphilis increased within two geographic core areas of infection and spread outward. A new core area of infection was established to the northwest. As the outbreak waned, density diminished and receded in all core areas. Morbidity remained elevated in the two original central and new northwestern core areas after the outbreak.

CONCLUSIONS

Density of syphilis infection was a simple informative measure easily compared across years. The BME approach was useful for quantitatively and qualitatively describing the spatial development and spread of syphilis. Our results are specific to Baltimore; however, the BME approach is generalizable to other settings and diseases.

HIV decline associated with behavior change in eastern Zimbabwe

Few sub-Saharan African countries have witnessed declines in HIV prevalence, and only Uganda has compelling evidence for a decline founded on sexual behavior change. We report a decline in HIV prevalence in eastern Zimbabwe between 1998 and 2003 associated with sexual behavior change in four distinct socioeconomic strata. HIV prevalence fell most steeply at young ages-by 23 and 49%, respectively, among men aged 17 to 29 years and women aged 15 to 24 years-and in more educated groups. Sexually experienced men and women reported reductions in casual sex of 49 and 22%, respectively, whereas recent cohorts reported delayed sexual debut. Selective AIDS-induced mortality contributed to the decline in HIV prevalence.

Dynamically modeling SARS and other newly emerging respiratory illnesses: past, present, and future

The emergence and rapid global spread of the severe acute respiratory syndrome (SARS) coronavirus in 2002-2003 prompted efforts by modelers to characterize SARS epidemiology and inform control policies. We overview and discuss models for emerging infectious diseases (EIDs), provide a critical survey of SARS modeling literature, and discuss promising future directions for research. We reconcile discrepancies between published estimates of the basic reproductive number R0 for SARS (a crucial epidemiologic parameter), discuss insights regarding SARS control measures that have emerged uniquely from a modeling approach, and argue that high priorities for future modeling of SARS and similar respiratory EIDs should include informing quarantine policy and better understanding the impact of population heterogeneity on transmission patterns.

Social and geographic distance in HIV risk

OBJECTIVE

The objective of this study was to examine the relationship between social distance (measured as the geodesic, or shortest distance, between 2 people in a connected network) and geographic distance (measured as the actual distance between them in kilometers [km]).

STUDY

We used data from a study of 595 persons at risk for HIV and their sexual and drug-using partners (total N = 8920 unique individuals) conducted in Colorado Springs, Colorado, from 1988 to 1992--a longitudinal cohort study that ascertained sociodemographic, clinical, behavioral, and network information about participants. We used place of residence as the geographic marker and calculated distance between people grouped by various characteristics of interest.

RESULTS

Fifty-two percent of all dyads were separated by a distance of 4 km or less. The closest pairs were persons who both shared needles and had sexual contact (mean = 3.2 km), and HIV-positive persons and their contacts (mean = 2.9). The most distant pairs were prostitutes and their paying partners (mean = 6.1 km). In a connected subset of 348 respondents, almost half the persons were between 3 and 6 steps from each other in the social network and were separated by a distance of 2 to 8 km. Using block group centroids, the mean distance between all persons in Colorado Springs was 12.4 km compared with a mean distance of 5.4 km between all dyads in this study (P <0.0001). The subgroup of HIV-positive people and their contacts was drawn in real space on a map of Colorado Springs and revealed tight clustering of this group in the downtown area.

CONCLUSION

The association of social and geographic distance in an urban group of people at risk for HIV provides demonstration of the importance of geographic clustering in the potential transmission of HIV. The proximity of persons connected within a network, but not necessarily known to each other, suggests that a high probability of partner selection from within the group may be an important factor in maintenance of HIV endemicity.

Evaluation of a cognitive-behavioral, group, randomized controlled intervention trial to prevent sexually transmitted infections and unintended pregnancies in young women

BACKGROUND

Few cognitive-behavioral interventions have focused on preventing sexually transmitted infections (STIs) and unintended pregnancies (UPs) in young, sexually active women in a single study. Military recruit training provides a well-defined, national, nonclinic sample in which to evaluate such an intervention.

METHODS

All female Marine recruits (N=2,288) in training were approached. Of these, 2,157 (94.3%) voluntarily agreed and were randomly assigned, by platoons, to participate in cognitive-behavioral interventions to prevent STIs or UPs or to prevent physical training injuries and cancer. Participants completed self-administered questionnaires and were screened for pregnancy, Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis at baseline and, on average, 1 and 14 months postintervention.

RESULTS

A higher proportion of the control group had a postintervention STI or UP [odds ratio (OR)=1.41, 95% confidence interval (CI)=1.01-1.98]. Among participants who had no history of STIs or pregnancy, but who engaged in risky sexual behaviors just before recruit training, the control group was more likely to acquire a postintervention STI (OR=3.24, CI=1.74-6.03). Among participants who were not sexually experienced at baseline, the control group was more likely to have casual (OR=2.05, 95% CI=1.04-4.08) and multiple (OR=1.87, 95% CI=1.01-3.47) sexual partners postintervention.

CONCLUSIONS

This randomized controlled trial indicates that cognitive-behavioral interventions are effective for reducing behavioral risk and preventing STIs and UPs in young, sexually active women who are not seeking health care.

Spatial analysis and mapping of sexually transmitted diseases to optimise intervention and prevention strategies

OBJECTIVE

We analysed and mapped the distribution of four reportable sexually transmitted diseases, chlamydial infection/non-gonococcal urethritis (chlamydial infection), gonorrhoea, primary and secondary syphilis (syphilis), and HIV infection, for Wake County, North Carolina, to optimise an intervention.

METHODS

We used STD surveillance data reported to Wake County, for the year 2000 to analyse and map STD rates. STD rates were mathematically represented as a spatial random field. We analysed spatial variability by calculating and modelling covariance functions of random field theory. Covariances are useful in assessing spatial patterns of disease locally and at a distance. We combined observed STD rates and appropriate covariance models using a geostatistical method called kriging, to predict STD rates and associated prediction errors for a grid covering Wake County. Final disease estimates were interpolated using a spline with tension and mapped to generate a continuous surface of infection.

RESULTS

Lower incidence STDs exhibited larger spatial variability and smaller neighbourhoods of influence than higher incidence STDs. Each reported STD had a clustered spatial distribution with one primary core area of infection. Core areas overlapped for all four STDs.

CONCLUSIONS

Spatial heterogeneity within STD suggests that STD specific prevention strategies should not be targeted uniformly across Wake County, but rather to core areas. Overlap of core areas among STDs suggests that intervention and prevention strategies can be combined to target multiple STDs effectively. Geostatistical techniques are objective, population level approaches to spatial analysis and mapping that can be used to visualise disease patterns and identify emerging outbreaks.