Epidemiological characteristics of scarlet fever in Nanjing during 2006-2015

Abstract

Objective To investigate the epidemiological characteristics and trends of scarlet fever in Nanjing from 2006 to 2015 for providing scientific evidence for making further strategy and measurements of prevention and control. Methods Descriptive epidemiological method was employed for epidemiological characteristics analysis of scarlet fever cases in Nanjing from 2006 to 2015. SaTScan9.4.1 was used for retrospective spatial scanning, ArcGIS10.2 was for drawing area distribution toward case numbers and incidence, and EpiInfo7.0 was for statistical analyses. Results Total 843 scarlet fever cases were reported in Nanjing during the period of 2006 to 2015. The average annual incidence was 1.15/100 000, and the reported incidence raised to 2.97/100 000 in 2015. The incidence peaked in April to July and November to February and accounted for 71.41% of the reported cases. The incidence of the disease in male was higher than that in female, and 94.90% of the cases were children under 15 years and the majorities were students and nursery children. The three districts in the north of the Yangtze River had higher reported incidence, in which the Chemical Industrial Park had an average annual incidence of 15.78/100 000 and that for 2015 was 52.24/100 000, which was much higher than other districts. Clusters were also occurred in the Chemical Industrial Park and the period was April 6, 2014 to December 31, 2015. Four adjacent streets stretched across the three districts in the north of the Yangtze River reported 53.02% of the cases in Nanjing and 79.54% of that in the three districts in the north of the Yangtze River. In the year of 2015, the Jiangbei People’s Hospital in Nanjing reported 71.07% cases in Nanjing, which increased significantly compared with 43.09% from 2006 to 2014 (χ2=54.05, P<0.001). Meanwhile, between 2006 and 2015, the Jiangbei People’s Hospital reported 89.02% of cases in the 4 streets with high incidence and 32.08% of cases in other streets/counties in the three districts in the north of the Yangtze River, with statistically significant difference (χ2=174.85, P<0.001) and 99.78% of the patients reported by the Jiangbei People’s Hospital resided in the three districts in the north of the Yangtze River. Conclusion The incidence of scarlet fever in Nanjing shows a rising trend; the Chemical Industrial Park is an area of high incidence; the increase of reported cases from the Jiangbei People’s Hospital might cause the growth of the overall incidence in Nanjing. It is suggested that we should conduct special investigation on the cause of high incidence and further strengthen surveillance, prevention and control measure in schools and kindergartens at the same time. Key words: Scarlet Fever; Group A β-hemolytic streptococcus; Epidemiological characteristics; Spatial-temporal clustering analysis