Epidemiological characteristics and spatial clustering of scrub typhus in Nanjing from 2011 to 2020 / 中华地方病学杂志

ABSTRACT

Objective:To understand the reported incidence level, change of the trend, epidemic characteristics and spatial clustering of scrub typhus in Nanjing, to explore key seasons, populations and areas for prevention and control, and to guide formulation of scientific and precise prevention and control strategies and measures.Methods:The reported data of scrub typhus in Nanjing from January 1, 2011 to December 31, 2020 were collected in the "Infectious Disease Surveillance System" from Chinese Center for Disease Control and Prevention. The reported incidence level and change of the trend were analyzed, and the seasonal, population and spatial distribution characteristics were described. Global spatial autocorrelation analysis was carried out by ArcGIS 10.3 software, and the spatial clustering scanning was carried out by using FleXScan 3.1.2 software.Results:A total of 192 cases of scrub typhus were reported in Nanjing from 2011 to 2020. Median annual reported incidence was 0.21/100 000 (0.12/100 000 - 0.49/100 000). Totally 87.5% (168/192) of cases were reported from October to November, and the peak occurred in November (57.8%, 111/192). Among these cases, males accounted for 64.1% (123/192); and the median age was 59 years old (6 - 84 years old). The groups ≥60 years old and 45 - 59 years old accounted for 47.9% (92/192) and 31.2% (60/192), respectively, which accounted for 79.2% (152/192) in all groups. Farmers accounted for 43.8% (84/192), household chores and unemployed people accounted for 16.7% (32/192), retired persons accounted for 15.6% (30/192) and workers accounted for 6.8% (13/192), which accounted for 82.8% (159/192) in all occupations. The top four areas in the total number of reported cases were Jiangning District (23.4%, 45/192), Luhe District (22.9%, 44/192), Gulou District (10.4%, 20/192) and Jiangbei New Area (8.9%, 17/192), which accounted for 65.6% (126/192) in all districts. According to global spatial autocorrelation analysis, Moran's I = 0.34 ( Z = 5.90, P < 0.001). FlexScan 3.1.2 software scanned and detected two spatial clusters areas, the first-class of cluster area covered three streets in Jiangning District, one street in Yuhuatai District and two streets in Pukou District [restricted log likelihood ratio ( RLLR) = 26.91, P < 0.001]. The second-class of cluster area included six townships/streets in Luhe District and four streets in Jiangbei New Area ( RLLR = 26.48, P < 0.001). All the cluster areas were agriculture-related. Conclusions:The reported incidence level of scrub typhus in Nanjing is low and stable which belongs to a typical autumn epidemic area. The middle-aged and elderly population is the key population and the agriculture-related area is key area. It is suggested that scrub typhus should be included in the management of statutory or regional key infectious diseases in Nanjing. Additionally, training on diagnosis and treatment technology and information report management of scrub typhus need to be carried out, and comprehensive prevention and control interventions such as health education, personal protection, rodent prevention and control and vector control should be strengthened and implemented in the high incidence season.