Prevalence characteristics and spatial clustering of Japanese B encephalitis in Jiangsu province, 2005 – 2018: a surveillance data analysis

  Objective  To analyze prevalence characteristics and spatial clustering of Japanese B encephalitis (JE) and the correlation between the occurrence of JE and the seasonal fluctuation of Culex tritaeniorhynchus in Jiangsu province during 2005 – 2018 for providing evidences to JE prevention.

  Methods  Data on reported JE cases and demographics in Jiangsu province during 2005 – 2018 were extracted from National Disease Control Information System and the data on Culex tritaeniorhynchus density in the province for years of 2008 – 2018 were collected from vector monitoring system. Descriptive statistics were used in data analyses.

  Results  Totally 495 JE cases were reported during the period in Jiangsu province and a decreasing trend in the annual JE incidence was observed (χ² = – 16.11, P < 0.01). Of all the reported cases, 92.73% were children aged 1 – 14 years. Obvious seasonal variation in JE incidence was detected and more cases were reported between 7th July and 7th September in a year (relative risk = 86.48, log likelihood ratio = 726.97; P < 0.01). The peak period of JE incidence was in July in South Jiangsu but in August in Northern Jiangsu. Purely spatial scan analysis results demonstrated the clustering of JE cases mainly in three cities in the northern and one city in the southern of Jiangsu province. For the period of 2008 – 2018, the monthly average number of JE cases statistically correlated with the lag day 30 monthly average density of Culex tritaeniorhynchus measured at live-stock sheds (r = 0.79, P < 0.01).

  Conclusion  The incidence of JE was closely related to the seasonal fluctuation of Culex tritaeniorhynchus density in Jiangsu province, suggesting that monitoring on Culex tritaeniorhynchus density and comprehensive anti-mosquito measures should be promoted, especially in regions with clustering of JE cases.