Estimating Epidemiological Disease Burden Of Syphilis Associated Adverse Pregnancy Outcomes And Spatial Distribution Of Congenital Syphilis In China

Background Syphilis can be transmitted from mother to infant during pregnancy or delivery,causing a variety of adverse pregnancy outcomes including early fetal loss,stillbirth,neonatal death,prematurity,low birth weight and clinical evidence of congenital syphilis.With the epidemics of syphilis,mother-to-child transmission of syphilis has become one of the major public health problems in China.China has been collecting case reporting data of congenital syphilis since the 1980s,however,China has been not collected the data of other syphilis associated adverse pregnant outcomes so far.In addition,there are problems of inaccurate case reporting due to the complicated diagnosis for congenital syphilis.Also lacking understandingof the spatial distribution of congenital syphilis.Therefore,estimating the epidemiological burden of syphilis associated adverse pregnancy outcomes and exploring the spatial distribution characteristics and patterns of congenital syphilis,are the key scientific problems which should be discussed and resolved in this article.Objectives To estimate national epidemiological burden of syphilis in pregnancy and associated adverse pregnancy outcomes(SP-APOs)in 31 provinces of China in 2015.Exploring the spatial distribution characteristics and patterns of congenital syphilis to accurately identify the hot spots over China.Comparing the differences between the estimated number and reporting number of congenital syphilis cases to evaluate case reporting accurate rate for congenital syphilis.Methods Collecting data of syphilis test,infection and treatment in county level from 31 provinces of China in 2015.The WHO-developed estimation model of syphilis in pregnancy and associated adverse pregnant outcomes(SP-APOs)was used to estimate the number of maternal syphilis and associated adverse pregnant outcomes.Meta analysis was applied to pool the syphilis test rate,positive rate and treatment rate of pregnant women in other counties of each city or each province to supplement the missing data.The geographic information system software GeoDa 1.12 and ArcGIS 10.0 were used to conduct global and local spatial autocorrelation analysis to explore the spatial distribution characteristics and patterns of congenital syphilis in county level.Meanwhile,the differences of case number and spatial distribution were compared between estimated and reporting epidemics of congenital syphilis.Results The estimation of SP-APOs burden was conducted in 2,675 counties of 337 cities in 30 provinces(data were not reported in Tibet Autonomous Region)of mainland China.In 2015,an estimated of 35,247 pregnant women were infected with syphilis and prevalence rate was 0.23%.It is estimated that a total of 5232 adverse pregnancy outcomes were caused by maternal syphilis infections,including 2,406 early fetal losses and stillbirths,928 neonatal deaths,788 preterm or low weight births,and 1,110 infected infants nationally.The overall incidence rate of syphilis associated adverse pregnant outcomes was 34.1/100,000 in China.There were great differences of incidence rates among provinces in China.The highest rate was 129.9/100,000 in Qinghai,and the lowest rate was 5.8/100,000 in Gansu.There were thirteen provinces were higher than national average rate,and ten of them were higher than 50 per 100,000.The results from further spatial analysis for estimated cases of congenital syphilis revealed that 32 hot-spots counties with more than 2 congenital syphilis cases were identified,and these counties were mainly distributed in 6 core areas,including west of Xinjiang,Haixi Mongolian and Tibetan Autonomous Prefecture and Golog Tibetan Autonomous Prefecture of Qinhai,middle of Jilin,south of Sichuan,north-east of Yunan and middle-west of Guizhou,south of Zhejiang and north-east of Fujian,and Guangzhou,etc.For reported cases of congenital syphilis,100 hot-spots counties with more than 9 congenital syphilis cases were identified,and these counties were mainly distributed in 5 core areas which includes almost the same provinces as the above areas.However,these areas were wider than the hot-spots areas for estimated cases of congenital syphilis.The results of comparing differences between the estimated number and reporting number of congenital syphilis cases showed that the reporting numbers were higher than the estimated number in all provinces expect Shanghai,and the national over-report proportion was 84.61%.The over-report proportions of all provinces were higher than 60%expect Shanghai,Zhejiang and Tianjin.The proportions of seven provinces were higher than 90%,and the highest was 96.49%in Shanxi.Conclusions For the first time,the WHO-developed SP-APOs model was used to estimate the national epidemiological burden of maternal syphilis and associated adverse pregnant outcomes in county level in China,indicating that the disease burden was relatively serious in some parts of China.Provinces where the incidence rates of syphilis associated adverse pregnant outcomes were higher than 50 per 100,000 were mainly distributed in northwestern,northeasten and southwestern China.Hot-spots counties in spatial analysis were also mainly distributed in these regions,which were the key areas for the prevention of mother-to-child transmission of syphilis in the future.Congenital syphilis cases only accounted for a small part of syphilis associated adverse pregnant outcomes.Therefore,it is necessary to collect data of early fetal loss,stillbirth and neonatal death,etc.that caused by maternal syphilis.Over-reporting of congenital syphilis is a major concern over China.Recommendations about strengthening on-site review of diagnosis and reporting for congenital syphilis in all provinces should be useful for accurate reporting of congenital syphilis.