Early Syphilis Among Men in Connecticut: Epidemiologic and Spatial Patterns

[Spatial analysis as a tool for identification of priority intervention areas for syphilis prevention]

The spatial analysis of syphilis constitutes a tool capable of contributing to the establishment of guidelines for action in priority geographic areas for preventive intervention. The scope of the article was to describe the scientific evidence that used geoprocessing as a tool to identify risk areas for syphilis. This is an integrative review of the literature, carried out in the Medline/PubMed, Scopus, Web of Science, Lilacs, Ibecs, Cochrane Library Portal, SciELO, Cuiden and Bdenf databases through cross-referencing between the key words "syphilis," "spatial analysis," "geographical information system," "health education" and "geographical mapping." A total of 13 articles were analyzed and in most of them syphilis cases were distributed in a heterogeneous manner, not obeying a unique epidemiological profile in relation to the units of analysis. Discordant ecological and spatial effects between syphilis and HIV and the viability of the integrated screening of syphilis with other diseases was revealed. Efficacy and ability of spatial analysis to target specific educational interventions for each reality were revealed, avoiding investment in geographically non-priority areas for syphilis control.

Influence of Detection Method and Study Area Scale on Syphilis Cluster Identification in North Carolina

BACKGROUND

Identifying geographical clusters of sexually transmitted infections can aid in targeting prevention and control efforts. However, detectable clusters can vary between detection methods because of different underlying assumptions. Furthermore, because disease burden is not geographically homogenous, the reference population is sensitive to the study area scale, affecting cluster outcomes. We investigated the influence of cluster detection method and geographical scale on syphilis cluster detection in Mecklenburg County, North Carolina.

METHODS

We analyzed primary and secondary syphilis cases reported in North Carolina (2003-2010). Primary and secondary syphilis incidence rates were estimated using census tract-level population estimates. We used 2 cluster detection methods: local Moran's I using an areal adjacency matrix and Kulldorff's spatial scan statistic using a variable size moving circular window. We evaluated 3 study area scales: North Carolina, Piedmont region, and Mecklenburg County. We focused our investigation on Mecklenburg, an urban county with historically high syphilis rates.

RESULTS

Syphilis clusters detected using local Moran's I and Kulldorff's scan statistic overlapped but varied in size and composition. Because we reduced the scale to a high-incidence urban area, the reference syphilis rate increased, leading to the identification of smaller clusters with higher incidence. Cluster demographic characteristics differed when the study area was reduced to a high-incidence urban county.

CONCLUSIONS

Our results underscore the importance of selecting the correct scale for analysis to more precisely identify areas with high disease burden. A more complete understanding of high-burden cluster location can inform resource allocation for geographically targeted sexually transmitted infection interventions.

Spatial epidemiology of the syphilis epidemic in Toronto, Canada

BACKGROUND

Urban centers across Canada and the United States have battled syphilis epidemics with high rates of human immunodeficiency virus (HIV) coinfection for over a decade. We examined the spatial epidemiology of syphilis over time for Toronto (Canada) with the intention of forming new insights and strategies for restoring low syphilis rates.

METHODS

Syphilis incidence rates, HIV-syphilis coinfection, and sexual risk behavior prevalences were estimated and mapped from primary, secondary, early latent syphilis cases reported to Toronto Public Health between January 1, 2006, and December 31, 2010, using ArcGIS 9.0. Geographic clusters of significantly elevated syphilis incidence rates were identified using SaTScan 9.0. The relationship between syphilis incidence rates and sociocultural factors was modeled using the Besag, York, and Mollie model.

RESULTS

Between 2006 and 2010, syphilis incidence rates were high in Toronto's downtown core area, intensified, and spread outward initiating 3 independent outbreak areas. HIV coinfection was high (47%); however, no spatial clustering was identified. Syphilis incidence rates, HIV coinfection, and behavioral risk factors promoting sexually transmitted infection transmission were high outside the core area, suggesting that peripheral sexual networks may be influencing high syphilis infection rates both inside and outside the core.

CONCLUSIONS

Toronto's syphilis epidemic is mature. Response, resources, and intervention activities should target core and noncore areas.

Spatial analysis of primary and secondary syphilis incidence in China, 2004-2010

China has recently experienced an increase in the incidence of syphilis. Effective spatial monitoring of syphilis incidence is important for successful implementation of control and prevention programmes. This study monitored county-level primary and secondary (P&S) syphilis incidence rates for all of mainland China by examining spatial patterns. Exploratory spatial data analysis (ESDA) methods were used to characterize the spatial distribution pattern of syphilis cases. During the seven-year study period, the average annual P&S syphilis incidence was 8.82 cases per 100,000 people. Using Empirical Bayes smoothed rates, the local Moran test identified many areas of high syphilis risk (all P values ≤0.01). The number of high-risk counties increased from 73 counties in 2004 to 134 counties in 2010. An eastern coastal cluster of high-risk counties persisted throughout 2004-2010. ESDA methods can assist public health officials in identifying high-risk areas. Allocating more resources to high-risk areas could more effectively reduce syphilis incidence.

Spatial analysis of county-based gonorrhoea incidence in mainland China, from 2004 to 2009

BACKGROUND

Gonorrhoea is one of the most common sexually transmissible infections in mainland China. Effective spatial monitoring of gonorrhoea incidence is important for successful implementation of control and prevention programs. The county-level gonorrhoea incidence rates for all of mainland China was monitored through examining spatial patterns.

METHODS

County-level data on gonorrhoea cases between 2004 and 2009 were obtained from the China Information System for Disease Control and Prevention. Bayesian smoothing and exploratory spatial data analysis (ESDA) methods were used to characterise the spatial distribution pattern of gonorrhoea cases.

RESULTS

During the 6-year study period, the average annual gonorrhoea incidence was 12.41 cases per 100000 people. Using empirical Bayes smoothed rates, the local Moran test identified one significant single-centre cluster and two significant multi-centre clusters of high gonorrhoea risk (all P-values <0.01).

CONCLUSIONS

Bayesian smoothing and ESDA methods can assist public health officials in using gonorrhoea surveillance data to identify high risk areas. Allocating more resources to such areas could effectively reduce gonorrhoea incidence.

Using spatial regression methods to examine the association between county-level racial/ethnic composition and reported cases of Chlamydia and gonorrhea: an illustration with data from the state of Texas

BACKGROUND

Several studies have reported racial/ethnic disparities in the incidence of sexually transmitted diseases. However, very few studies have accounted for potential spatial dependence. Additionally, little is known about the relative magnitudes of the associations between county-level racial/ethnic composition and the 2 most commonly reported sexually transmitted diseases.

METHODS

We used county-level data from the National Electronic Telecommunications System for Surveillance and the 2000 Census data to investigate the association between county-level racial/ethnic composition and reported cases of the 2 most commonly reported sexually transmitted diseases (chlamydia and gonorrhea) in Texas. We also estimated ordinary least square (OLS) models for comparison.

RESULTS

Preliminary results from the spatial regression models indicated that the choice of spatial relationships criteria was important for model specification. The spatial error model (SEM) was superior to the spatial autoregressive model, spatial Durbin model, and OLS. The SEM for the 2 disease equations were further analyzed using a seemingly unrelated regression estimation (SURE) procedure. Although the SEM was superior to all models (using standard criteria), the coefficients were fairly stable across models. Our results showed that a unit change in percent black was associated with 1.6 (1.1 for Hispanic) and 3.3 (0.5 for Hispanic) percent change in chlamydia and gonorrhea rates (on average), respectively, compared with percent white.

CONCLUSION

Although there were no substantial differences in the magnitude of the estimated parameters, spatial regression models are potentially superior to OLS models and should be explored in future sexually transmitted disease studies.

Monitoring county-level chlamydia incidence in Texas, 2004 - 2005: application of empirical Bayesian smoothing and Exploratory Spatial Data Analysis (ESDA) methods

BACKGROUND

Chlamydia continues to be the most prevalent disease in the United States. Effective spatial monitoring of chlamydia incidence is important for successful implementation of control and prevention programs. The objective of this study is to apply Bayesian smoothing and exploratory spatial data analysis (ESDA) methods to monitor Texas county-level chlamydia incidence rates by examining spatiotemporal patterns. We used county-level data on chlamydia incidence (for all ages, gender and races) from the National Electronic Telecommunications System for Surveillance (NETSS) for 2004 and 2005.

RESULTS

Bayesian-smoothed chlamydia incidence rates were spatially dependent both in levels and in relative changes. Erath county had significantly (p < 0.05) higher smoothed rates (> 300 cases per 100,000 residents) than its contiguous neighbors (195 or less) in both years. Gaines county experienced the highest relative increase in smoothed rates (173% - 139 to 379). The relative change in smoothed chlamydia rates in Newton county was significantly (p < 0.05) higher than its contiguous neighbors.

CONCLUSION

Bayesian smoothing and ESDA methods can assist programs in using chlamydia surveillance data to identify outliers, as well as relevant changes in chlamydia incidence in specific geographic units. Secondly, it may also indirectly help in assessing existing differences and changes in chlamydia surveillance systems over time.

Epidemiology of infectious syphilis in Ottawa. Recurring themes revisited

OBJECTIVES

To describe the epidemiology of an outbreak of infectious syphilis in Ottawa.

METHODS

A retrospective chart review of infectious syphilis cases in Ottawa from 2001-2006.

RESULTS

Rates of syphilis have risen more than tenfold. The epidemic was centered in men, with the majority of cases (83.5%) occurring among men who have sex with men (MSM). These individuals differed from the general MSM population residing in Ottawa in their being older, more likely to be HIV positive, and more sexually promiscuous. Inconsistent condom use by MSM engaged in either oral or anal sex was pervasive. Thirty-seven percent of MSM reported sexual encounters with men from Montreal and Toronto. Visceral manifestations of syphilis, including neurosyphilis, were more common in persons co-infected with HIV. As a result, this subgroup was more likely to have received an extended antibiotic treatment regimen. There was a substantial delay between serological diagnosis and treatment. Less than half of treated cases returned for a six-month evaluation.

CONCLUSIONS

Multiple sexual partners, unprotected oral sex, and increased age among MSM were the predominant risk factors contributing to this syphilis epidemic. Co-infection with HIV modified the clinical presentation of syphilis, necessitating a more intensive diagnostic and therapeutic approach. The interconnection of urban sexual networks has likely contributed to the dynamics of local syphilis transmission and suggests that effective interventions will require a coordinated national approach.

Sex partner meeting venues and out-of-state sex partners among men who have sex with men with early syphilis in Connecticut

OBJECTIVES

To examine sex partner meeting venues and out-of-state sex partners among men who have sex with men (MSM) with syphilis in Connecticut, a state with moderate syphilis prevalence.

GOAL

To better understand transmission dynamics in the current syphilis epidemic.

STUDY DESIGN

Review of health department records.

RESULTS

A total of 185 MSM were diagnosed with early syphilis in Connecticut from 2000 to 2005 (mean age, 36 years; 56% white, 37% HIV-positive). Fifty-two percent of cases reported meeting sex partners at venues that facilitate multiple and/or anonymous sexual encounters including gay clubs or bars (22%), Internet (18%), and adult bookstores (12%). Meeting sex partners in venues increased over time and was associated with nonmetropolitan residence of the case. Forty-three percent of cases had an out-of-state sex partner during the time in which they likely acquired their infection. Having out-of-state sex partners decreased during the study period. Throughout 2000-2005, having out-of-state sex partners was positively associated with bathhouse use and negatively associated with use of adult bookstores.

CONCLUSIONS

The observed pattern of increased meeting sex partners in venues located within the state and decreased out-of-state sex partners over time is suggestive of increasing transmission within the state of Connecticut.