CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES >

2025 , Vol. 43 >Issue 1: 147 - 151

DOI: https://doi.org/10.12140/j.issn.1000-7423.2025.01.024

SHORT COMMUNICATIONS

Seasonal characteristics of scrub typhus in Baoshan City using concentration ratio and circular distribution methods

  • LI Yanping ,
  • SHUI Tiejun ,
  • HE Kai ,
  • YANG Hexian ,
  • ZHAO Lijuan ,
  • YANG Xiaoling ,
  • DUAN Lizhong ,
  • WANG Liming ,
  • HUANG Dongsheng
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  • 1 Baoshan Prefecture Center for Disease Control and Prevention, Baoshan 678000, Yunnan, China
    2 Yunnan Provincial Center for Disease Control and Prevention, Kunming 650000, Yunnan, China

Received date: 2024-07-05

  Revised date: 2024-09-14

  Online published: 2025-03-26

Supported by

XingBao Talent Cultivation Program(2023023)

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Abstract

A statistical analysis was performed on the scrub typhus surveillance data in Baoshan City, Yunnan Province from January 1, 2017 to December 31, 2023 reported to the Chinese Disease Prevention and Control Information System. The concentration ratio (M value) of scrub typhus was calculated to analyze the seasonal distribution characteristics, and the day of the peak incidence of scrub typhus and epidemic peaks of scrub typhus were estimated using the circular distribution method. A Pearson correlation analysis was performed on the M value and the concentration parameter (r value) of a circular distribution. A total of 11 537 cases with scrub typhus were reported in Baoshan City from 2017 to 2023, with an annual reported incidence rate of 65.12/105, and the highest incidence in 2023 (96.71/105), and the incidence appeared an overall tendency towards a rise from 2017 to 2023 (χ2 = 484.882, P < 0.01). Farmers were the primary occupation among all cases with scrub typhus (78.79%, 9 090/11 537), and the reported scrub typhus cases are concentrated during the period between July and October from 2017 to 2023, with the highest proportion of reported cases in August each year, and the numbers of reported scrub typhus cases accounted for 26.74%, 33.13%, 34.25%, 32.84%, 34.55%, 27.17% and 39.34% of total cases each year from 2017 to 2023, which accounted for 33.04% (3 812/11 537) of total cases. The radar chart appeared a unimodal distribution in each year and each month, which met the prerequisite for concentration ratio and circular distribution analyses. The M value of total scrub typhus cases was 0.779 from 2017 to 2023, with 0.729 to 0.814 each year during the study period, indicating a strong seasonality of scrub typhus incidence in Baoshan City. The r value of the circular distribution of scrub typhus incidence was 0.758, with $\bar{\alpha } $ of 227.38° (184.89°, 269.87°) (Z = 6 626.66, P < 0.001) indicating the day of peak incidence on August 21, and epidemic peak during the period from July 6 to September 30. In addition, Pearson correlation analysis revealed a strong positive correlation between the M value and r value (Pearson coefficient was 0.940 and P was 0.001 65).

Key words： Scrub typhus; Seasonal distribution; Concentration ratio; Circular distribution method

Cite this article

LI Yanping , SHUI Tiejun , HE Kai , YANG Hexian , ZHAO Lijuan , YANG Xiaoling , DUAN Lizhong , WANG Liming , HUANG Dongsheng . Seasonal characteristics of scrub typhus in Baoshan City using concentration ratio and circular distribution methods[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2025 , 43(1) : 147 -151 . DOI: 10.12140/j.issn.1000-7423.2025.01.024

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