A spatial analysis of county-level variation in syphilis and gonorrhea in Guangdong Province, China

Preconception syphilis seroprevalence and association with duration of marriage and age among married individuals in Guangdong Province, China: A population-based cross-sectional study

BACKGROUND

Duration of marriage (DoM) and age are important characteristics of married individuals, who are the critical population for eliminating mother-to-child transmission (MTCT) of syphilis. A deep understanding of the preconception syphilis seroprevalence (PSS) and its distribution among this population may be able to help to eliminate MTCT. However, few population-based epidemiological studies have been focused on this group, and the association of DoM and age with PSS remains unclear.

METHODOLOGY/PRINCIPAL FINDINGS

This study used data from 4,826,214 married individuals aged 21-49 years who participated in the National Free Preconception Health Examination Project in Guangdong Province, China, between 2014 and 2019. Syphilis was screened using the rapid plasma reagin (RPR) test. The seroprevalence time series, seroprevalence map, and hot spot analysis (HSA) were employed to visualize the spatiotemporal distribution. The restricted cubic spline (RCS) based on multivariate logistic regression was used to model the association of DoM and age with PSS. The interactions on the additive scale of DoM and age were also assessed. The PSS was 266.61 per 100,000 persons (95% CI: 262.03-271.24) and the burden was higher in economically underdeveloped area within the province. A strong J-shaped non-linearity association was observed between age and PSS. Specifically, the risk of seropositivity was relatively flat until 27 years of age among men and increased rapidly afterwards, with an adjusted odds ratio (aOR) of 1.13 (95% CI: 1.12-1.13) per unit. Among women, the risk of seropositivity was relatively flat until 25 years of age and increased rapidly afterwards with an aOR of 1.08 (95% CI: 1.08-1.09) per unit. DoM was negatively associated with PSS among married individuals. Moreover, the combined effects of age and DoM appeared to be synergistic.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that attention should be paid to preventing syphilis in underdeveloped areas and that syphilis screening in newly married individuals who are in their late 20s or older should be recommended. Additionally, early syphilis prevention strategies should be implemented among young people as early as possible.

Spatiotemporal distribution and sociodemographic and socioeconomic factors associated with primary and secondary syphilis in Guangdong, China, 2005-2017

Background

Previous studies exploring the factors associated with the incidence of syphilis have mostly focused on individual-level factors. However, recent evidence has indicated that social-level factors, such as sociodemographic and socioeconomic factors, also affect the incidence of syphilis. Studies on the sociodemographic and socioeconomic factors associated with syphilis incidence are scarce, and they have rarely controlled for spatial effects, even though syphilis shows spatial autocorrelation.

Methodology/Principal findings

Syphilis data from 21 cities in Guangdong province between 2005 and 2017 were provided by the National Notifiable Infectious Disease Reporting Information System. The incidence time series, incidence map, and space-time scanning data were used to visualize the spatiotemporal distribution. The spatial panel data model was then applied to explore the relationship between sociodemographic factors (population density, net migration rate, male:female ratio, and the number of health institutions per 1,000 residents), socioeconomic factors (gross domestic product per capita, the proportion of secondary/tertiary industry), and the incidence of primary and secondary syphilis after controlling for spatial effects. The incidence of syphilis increased slowly from 2005 (11.91 per 100,000) to 2011 (13.42 per 100,000) and then began to decrease, reaching 6.55 per 100,000 in 2017. High-risk clusters of syphilis tended to shift from developed areas to underdeveloped areas. An inverted U-shaped relationship was found between syphilis incidence and gross domestic product per capita. Moreover, syphilis incidence was significantly associated with population density (β = 2.844, P = 0.006), the number of health institutions per 1,000 residents (β = -0.095, P = 0.007), and the net migration rate (β = -0.219, P = 0.002).

Conclusions/Significance

Our findings suggest that the incidence of primary and secondary syphilis first increase before decreasing as economic development increases further. These results emphasize the necessity to prevent syphilis in regions at the early stages of economic growth.

Syphilis is a sexually transmitted infection that continues to cause morbidity and mortality worldwide. The primary and secondary stages of syphilis are the most transmissive stages in the entire process of the disease. We analyzed primary and secondary (P&S) syphilis data from 2005 to 2017 in Guangzhou, China, provided by the National Notifiable Infectious Disease Reporting Information System. The results showed that the annual incidence rates of P&S syphilis slightly increased from 2005 to 2011 and then began to decrease in 2017. Cases of P&S syphilis were spatially clustered. The high-risk syphilis clusters tended to shift from developed areas to underdeveloped areas. There may be an inverted U-shaped relationship between the level of economic development and the incidence of P&S syphilis, suggesting that the incidence of P&S syphilis first increased before decreasing as the level of economic development increased further. These results emphasize the necessity of preventing syphilis at locations in the early stage of economic growth. Investments in syphilis prevention education for people in regions at early development stages may mitigate the increasing cost of syphilis to future healthcare systems.

Spatiotemporal analysis of 11 years of Chlamydia trachomatis data from southern China

BACKGROUND

Urogenital Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection (STI) globally. Reviews suggest high and persistently endemic STI epidemics in low and middle income countries. However population-based prevalence estimates in these settings are less common, underscoring the need for analyses of available data to characterize patterns of disease burden. We identified spatio-temporal clusters and key behavioral, social, or environmental factors contribution to transmission in order to inform the prioritization and targeting of evidence based interventions.

METHODS

Using 11 years of data (2006-2016) from the chlamydia case report system of Guangdong, China, we identified county level spatio-temporal hot and cold spots using the Getis-Ord Gi* statistic and discrete Poisson models in SaTScan 9.6. We also estimated associations between observed distribution patterns and area-level demographic, social, and economic factors using quasi-Poisson regression models that controlled for annual counts of certified laboratories to account for fluctuations in location-specific detection capacity.

FINDINGS

Cluster analysis indicates an expanding chlamydia epidemic in Guangdong, with cases clustered in regions of greatest economic activity. Greater male-to-female sex ratio (RR, 3.63; 95% CI, 1.41-9.45) and greater urbanicity (RR, 2.44; 95% CI, 1.98-2.99) were predictive of higher chlamydia case occurrence.

INTERPRETATION

We found that chlamydia case occurrence in Guangdong province has been accelerating over the past 11 years and that its expansion is tied to indicators of social and economic development. These estimates not only identify high prevalence regions to target but also areas where data gaps potentially remain. The salience of sex ratios and urbanicity may best be understood through the lens of China's modern history of labor migration which has reshaped the gender dynamics and health access landscape of urban China. Future chlamydia control efforts will require a population-based approach focused on reengaging sexually active adults of diverse economic and migratory backgrounds.

FUNDING

This was an unfunded study using routinely collected public health data.

Exploring spatially varying demographic associations with gonorrhea incidence in Baltimore, Maryland, 2002-2005

The ability to establish spatial links between gonorrhea risk and demographic features is an important step in disease awareness and more effective prevention techniques. Past spatial analyses focused on local variations in risk, but not on spatial variations in associations with demographics. We collected data from the Baltimore City Health Department from 2002 to 2005 and evaluated demographic features known to be associated with gonorrhea risk in Baltimore, by allowing spatial variation in associations using Poisson geographically weighted regression (PGWR). The PGWR maps revealed variations in local relationships between race, education, and poverty with gonorrhea risk which were not captured previously. We determined that the PGWR model provided a significantly better fit to the data and yields a more nuanced interpretation of "core areas" of risk. The PGWR model's quantification of spatial variation in associations between disease risk and demographic features provides local and demographic structure to core areas of higher risk.

Association of Neighborhood Geographic Spatial Factors With Rates of Childhood Obesity

IMPORTANCE

Childhood obesity is a principal public health concern. Understanding the geographic distribution of childhood obesity can inform the design and delivery of interventions.

OBJECTIVE

To better understand the causes of spatial dependence in rates of childhood obesity across neighborhoods.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from a legislatively mandated body mass index screening program for public school children in Arkansas from the 2003-2004 through 2014-2015 academic years. Spatial autoregressive moving average (SARMA) models for panel data were used to estimate spatial dependency in childhood obesity at 2 levels of spatial aggregation. Data were analyzed from August 2017 to February 2018.

EXPOSURES

The SARMA models included geographic fixed effects to capture time-invariant differences in neighborhood characteristics along with controls for the mean age of children and the proportion of children by race/ethnicity, school meal status, and sex.

MAIN OUTCOMES AND MEASURES

The proportion of obese schoolchildren in Arkansas neighborhoods by year, defined at larger (census tract) and smaller (census block group) spatial scales.

RESULTS

The geographic aggregations were based on 935 800 children with a mean (SD) age of 132 (39) months. Of these children, 51% were male; 65% were white, 21% were black, 10% were Hispanic, 2% were Asian, and the remainder were of other or unidentified race/ethnicity. In models without geographic fixed effects, there was evidence of positive and significant spatial autocorrelation in obesity rates across tracts (ρ = 0.511; 95% CI, 0.469-0.553) and block groups (ρ = 0.569; 95% CI, 0.543-0.595). When geographic fixed effects were included, spatial autocorrelation diminished at the census tract level (ρ = 0.271; 95% CI, 0.147-0.396) and disappeared at the census block group level (ρ = -0.075; 95% CI, -0.264 to 0.114).

CONCLUSIONS AND RELEVANCE

Because block groups are smaller than tracts, children in neighboring block groups were more likely to attend the same schools and interact through neighborhood play. Thus, geographic-based social networks were more likely to span block group boundaries. The lack of evidence of spatial autocorrelation in block group-level models suggests that social contagion may be less important than differences in neighborhood context across space. Caution should be used in interpreting significant spatial autocorrelation as evidence of social contagion in obesity.

Spatiotemporal distribution and determinants of gonorrhea infections in mainland China: a panel data analysis

OBJECTIVES

Gonorrhea remains a major public health concern worldwide. This study aims to explore the spatiotemporal distribution and sociodemographic determinants of gonorrhea rates during 2004-2014 in mainland China.

STUDY DESIGN

Space-time scan statistics and spatial panel regression model.

METHODS

The gonorrhea infection data and sociodemographic data during 2004-2014 at the provincial level in mainland China were extracted from the China Public Health Science Data Center and China Statistical Yearbooks, respectively. The space-time scan statistics were used to identify the high-risk clusters of gonorrhea, and the spatial panel regression model was adopted to examine the sociodemographic determinants.

RESULTS

One most likely and five secondary high-risk clusters of gonorrhea rates were identified, which were mainly located in southern and eastern China. The regions with higher GDP per capita, larger floating population, less access to healthcare, higher male-female ratio, and higher divorce rate were more likely to become high-risk areas of gonorrhea.

CONCLUSIONS

Gonorrhea rates were distributed unevenly through space and time and affected by various sociodemographic variables. The space-time scan statistics and spatial panel regression are viable tools for identifying clusters and examining determinants of gonorrhea rates. The findings provide valuable implications for developing targeted prevention and control programs in public health practice.

Landscape of emerging and re-emerging infectious diseases in China: impact of ecology, climate, and behavior

For the past several decades, the infectious disease profile in China has been shifting with rapid developments in social and economic aspects, environment, quality of food, water, housing, and public health infrastructure. Notably, 5 notifiable infectious diseases have been almost eradicated, and the incidence of 18 additional notifiable infectious diseases has been significantly reduced. Unexpectedly, the incidence of over 10 notifiable infectious diseases, including HIV, brucellosis, syphilis, and dengue fever, has been increasing. Nevertheless, frequent infectious disease outbreaks/events have been reported almost every year, and imported infectious diseases have increased since 2015. New pathogens and over 100 new genotypes or serotypes of known pathogens have been identified. Some infectious diseases seem to be exacerbated by various factors, including rapid urbanization, large numbers of migrant workers, changes in climate, ecology, and policies, such as returning farmland to forests. This review summarizes the current experiences and lessons from China in managing emerging and re-emerging infectious diseases, especially the effects of ecology, climate, and behavior, which should have merits in helping other countries to control and prevent infectious diseases.

The association between human perceived heat and early-stage syphilis and its variance: Results from a case-report system

BACKGROUND

The relationship between temperature and syphilis is poorly understood despite clues and suggestions from previous studies. We examined the association between human perceived temperature (humidex) and the relative risk of early-stage syphilis in the most affected area of China, as well as its variance across social-economic status and age groups.

METHODS

Information regarding early-stage (primary and secondary) syphilis cases reported to the China Case Report System between 2005-2013 from Guangdong province was analyzed in this study. Weather data were obtained from the National Meteorological Information Center. Distributed lag nonlinear models were applied to assess the relationship between humidex and the relative risk of early-stage syphilis. Results were further stratified by social-economic status and age groups.

RESULTS

The relative risks of early-stage syphilis mainly increased with increased humidex, and were elevated when the humidex was around 30 or greater than 38. The humidex-RR association for the 15-40 age group was similar to the scenario pooled across the age groups, particularly in the Pearl-River Delta Region. The relative risk of syphilis in the elderly for the non-Pearl-River Delta Region did not show a clear change with humidex, whereas that in the Pearl-River Delta Region substantially increased, particularly when humidex was above 25.

CONCLUSIONS

Human perceived temperature was positively related to the relative risk of early-stage syphilis. People in the Pearl-River Delta Region tended to be more sensitive, with relative risk elevated at potential comfortable times or under excessively hot conditions. The vulnerability of the elderly in the Pearl-River Delta Region is concerning.

Multivariate time series analysis on the dynamic relationship between Class B notifiable diseases and gross domestic product (GDP) in China

The surveillance of infectious diseases is of great importance for disease control and prevention, and more attention should be paid to the Class B notifiable diseases in China. Meanwhile, according to the International Monetary Fund (IMF), the annual growth of Chinese gross domestic product (GDP) would decelerate below 7% after many years of soaring. Under such circumstances, this study aimed to answer what will happen to the incidence rates of infectious diseases in China if Chinese GDP growth remained below 7% in the next five years. Firstly, time plots and cross-correlation matrices were presented to illustrate the characteristics of data. Then, the multivariate time series (MTS) models were proposed to explore the dynamic relationship between incidence rates and GDP. Three kinds of MTS models, i.e., vector auto-regressive (VAR) model for original series, VAR model for differenced series and error-correction model (ECM), were considered in this study. The rank of error-correction term was taken as an indicator for model selection. Finally, our results suggested that four kinds of infectious diseases (epidemic hemorrhagic fever, pertussis, scarlet fever and syphilis) might need attention in China because their incidence rates have increased since the year 2010.

Epidemiological and Ecological Characterization of the EHEC O104:H4 Outbreak in Hamburg, Germany, 2011

In 2011, a large outbreak of entero-hemorrhagic E. coli (EHEC) and hemolytic uremic syndrome (HUS) occurred in Germany. The City of Hamburg was the first focus of the epidemic and had the highest incidences among all 16 Federal States of Germany. In this article, we present epidemiological characteristics of the Hamburg notification data. Evaluating the epicurves retrospectively, we found that the first epidemiological signal of the outbreak, which was in form of a HUS case cluster, was received by local health authorities when already 99 EHEC and 48 HUS patients had experienced their first symptoms. However, only two EHEC and seven HUS patients had been notified. Middle-aged women had the highest risk for contracting the infection in Hamburg. Furthermore, we studied timeliness of case notification in the course of the outbreak. To analyze the spatial distribution of EHEC/HUS incidences in 100 districts of Hamburg, we mapped cases' residential addresses using geographic information software. We then conducted an ecological study in order to find a statistical model identifying associations between local socio-economic factors and EHEC/HUS incidences in the epidemic. We employed a Bayesian Poisson model with covariates characterizing the Hamburg districts as well as incorporating structured and unstructured spatial effects. The Deviance Information Criterion was used for stepwise variable selection. We applied different modeling approaches by using primary data, transformed data, and preselected subsets of transformed data in order to identify socio-economic factors characterizing districts where EHEC/HUS outbreak cases had their residence.

The increase of sexually transmitted infections calls for simultaneous preventive intervention for more effectively containing HIV epidemics in China

OBJECTIVE

To identify the priority public health challenges with respect to the development of multipurpose prevention technologies in China.

DESIGN

Review of published literature, databases of state and local disease control agencies and unpublished data relating to HIV and other sexually transmitted infections (STIs).

SETTING

China.

POPULATION

General and migrant populations.

METHODS

Review of published data, government reports and databases of China Disease Control agencies, and our unpublished studies.

MAIN OUTCOME MEASURES

Reported STI incidence, particularly HIV, syphilis, chlamydia and genital herpes, and the migrant population with respect to disease transmission.

RESULTS

We found that the reported STI incidence increases along with that of HIV and showed significant geographic overlap with HIV. Economic migrant workers may facilitate the spread of STIs, including HIV.

CONCLUSIONS

To more effectively contain the HIV epidemic, it is imperative to develop preventive measures to simultaneously target HIV and other STIs. We recommend that the development of multipurpose prevention technologies in China should target HIV and STIs.

Social determinants of syphilis in South China: the effect of sibling position on syphilis and sexual risk behaviours

OBJECTIVE

This study evaluated the relationship between sibling position and sexual risk based on behavioural and syphilis infection data from sexually transmitted infection (STI) patients in South China.

DESIGN

A cross-sectional study examining sexual behaviours and syphilis infection.

SETTING

4 STI clinics in the Pearl River Delta of South China.

PARTICIPANTS

1792 Chinese men and women attending STI clinics.

PRIMARY OUTCOME MEASURES

STI history, syphilis infection defined as positive non-treponemal and treponemal tests.

RESULTS

Among all clinic patients, 824 (46.3%) were first-born, 354 (19.9%) were middle-born and 602 (33.8%) were final-born. Middle-born individuals had a higher percentage of reported STI history (44.7% compared to 34.7%, p<0.001) and syphilis infection (9.7% compared to 4.9%, p=0.01) among men (n=1163) compared to other sibling positions in bivariate analyses, but not in the final multivariate model. The relationship between sibling position and syphilis was independent of income and education level. There was no trend observed between middle-born position and female sexual risk behaviours (n=626). Higher education was significantly associated with syphilis among women and men in respective multivariate models.

CONCLUSIONS

This study suggests that middle-born men in China may have an increased sexual risk compared to other sibling positions. As Chinese family and social structures change, a more thorough understanding of how demographic factors influence sexual risk behaviours is needed.

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.

Multilevel and spatial analysis of syphilis in Shenzhen, China, to inform spatially targeted control measures

OBJECTIVES

The present study investigates the varied spatial distribution of syphilis cases in Shenzhen, China, and explores the individual-, neighbourhood- and district-level factors affecting the distribution.

METHODS

This study uses spatial analysis and multi-level generalised estimating equations to explore the spatial distribution of reported syphilis cases among individuals in Shenzhen, Guangdong Province, China. The spatial distribution of primary/secondary and latent cases was investigated using the Moran's I-statistic. Primary/secondary syphilis cases were compared with all syphilis cases using a three-level model with individual (n=6496), neighbourhood (n=55) and district (n=6) levels.

RESULTS

A total of 6496 syphilis cases were reported in 2009 with 35.8% primary and secondary syphilis cases. Both primary/secondary syphilis cases (Moran's I value=0.33, p<0.01) and latent syphilis cases (Moran's I value=0.19, p<0.01) showed significant spatial clustering at the neighbourhood level. Adjusting for the number of reporting hospitals, the best model found that the following characteristics were associated with primary/secondary syphilis infection: individuals who are younger in age (p=0.003), male (p<0.001), migrant labourers (p=0.047) and those who live in districts with a higher gross domestic product (p<0.001).

CONCLUSIONS

There is substantial clustering of primary and secondary syphilis cases at the neighbourhood level in Shenzhen, suggesting the need for greater STD health service provision in these clustered neighbourhoods. Spatially targeted syphilis control measures may be useful to optimise testing, treatment and partner services.

The effect of a structural intervention for syphilis control among 3597 female sex workers: a demonstration study in South China

BACKGROUND

Syphilis has made a rapid resurgence in China, especially among high-risk groups including female sex workers (FSWs).

METHODS

Two cities in each of 3 provinces in South China were chosen and allocated to intervention or control arms. The intervention consisted of enhancing community-based syphilis screening outreach intervention with comprehensive sexually transmitted infection services at designated clinics while the control maintained routine intervention activities. Generalized linear modeling was used to examine effect of the intervention on incident syphilis infection.

RESULTS

A total of 8275 women were eligible, and 3597 women enrolled (n = 2011 in control arm, n = 1586 in intervention arm) in the study. The median follow-up duration was 375 days (interquartile range, 267–475). Syphilis incidence density in the intervention group was reduced by 70% (95% confidence interval, 53%–81%) compared with the incidence in the control arm. The syphilis prevention intervention benefits were robust among FSWs at low-tier venues, individuals with less than high school education, migrants, and women who did not report condom use during the last episode of sex.

CONCLUSIONS

Integrated sexually transmitted infection and human immunodeficiency virus prevention strategies substantially reduce syphilis incidence among FSWs, especially among those at low-tier venues. This intervention suggests the need for scaling up comprehensive FSW programs in China.

A twin response to twin epidemics: integrated HIV/syphilis testing at STI clinics in South China

BACKGROUND

HIV testing is still stigmatized among many high-risk groups in China, whereas routine syphilis testing has been widely accepted at sexually transmitted infection (STI) clinics. This project used the platform of a rapid syphilis screening test to expand HIV test uptake. The objective of this study was to use multilevel modeling to analyze determinants of syphilis and HIV-testing uptake at STI clinics in China.

METHODS

2061 STI patients at 6 clinics in Guangdong Province were offered free rapid syphilis and free rapid HIV testing. Test uptake was defined by patient receipt of results and a multilevel model was used to analyze predictors of uptake.

RESULTS

This was the first syphilis or HIV test for the large majority (1388, 77.7%) of participants. Syphilis test uptake and HIV test uptake were high (1681, 81.6%, syphilis test uptake; 1673, 81.2% HIV test uptake). HIV test uptake was significantly concordant with syphilis test uptake (τb = 0.89, P < 0.001). The most parsimonious model of refusing HIV test uptake included the following variables: being married, having a previous HIV test, being unaccompanied, and participating in the last 2 months of the study.

CONCLUSIONS

STI clinic-based screening for syphilis and HIV represents an excellent opportunity for scaling up integrated services, especially in South China where syphilis and sexually transmitted HIV cases are both rapidly increasing. Effective integration of HIV testing into routine clinical practice requires an understanding not only of individual test uptake but also of the broader social context of HIV testing.