Open Access Research article

Clinical characteristics of the autumn-winter type scrub typhus cases in south of Shandong province, northern China

Yun-Xi Liu1*, Dan Feng2, Ji-Jiang Suo1, Yu-Bin Xing1, Gang Liu3, Li-Hua Liu2, Hong-Ju Xiao3, Ning Jia1, Yan Gao1, Hong Yang4, Shu-Qing Zuo4, Pan-He Zhang4, Zhong-Tang Zhao5, Jing-Si Min6, Pei-Tian Feng7, Shu-Bin Ma8, Song Liang9* and Wu-Chun Cao4*

Author Affiliations

1 Department of Nosocomial Infection Management and Disease Control, Institute of Hospital Management, Chinese People's Liberation Army General Hospital, Chinese People's Liberation Army Postgraduate Medical School, Beijing 100853, PR China

2 Department of Health Statistics, Institute of Hospital Management, Chinese People's Liberation Army General Hospital, Chinese People's Liberation Army Postgraduate Medical School, Beijing 100853, PR China

3 Department of Febrile Disease, Chinese People's Liberation Army General Hospital, Chinese People's Liberation Army Postgraduate Medical School, Beijing 100853, PR China

4 State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China

5 School of Public Health, Shandong University, Jinan 250012, PR China

6 Department of Internal Medicine, Wanggou Township Hospital, Feixian County, Shandong Province 273408, PR China

7 Department of Internal Medicine, Shangye Township Hospital, Feixian County, Shandong Province 273401, PR China

8 Department of Internal Medicine, Fangcheng Township Hospital, Feixian County, Shandong Province 273409, PR China

9 College of Public Health, The Ohio State University, Columbus, Ohio 43210, USA

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BMC Infectious Diseases 2009, 9:82  doi:10.1186/1471-2334-9-82

Published: 4 June 2009

Abstract

Background

Before 1986, scrub typhus was only found endemic in southern China. Because human infections typically occur in the summer, it is called "summer type". During the autumn-winter period of 1986, a new type of scrub typhus was identified in Shandong and northern Jiangsu province of northern China. This newly recognized scrub typhus was subsequently reported in many areas of northern China and was then called "autumn-winter type". However, clinical characteristics of associated cases have not been reported.

Methods

From 1995 to 2006, all suspected scrub typhus cases in five township hospitals of Feixian county, Shandong province were enrolled. Indirect immunofluorescent assay (IFA) was used as confirmatory serodiagnosis test. Polymerase chain reaction (PCR) connected with restriction fragment length polymorphism (RFLP) and sequence analyses were used for genotyping of O. tsutsugamushi DNAs. Clinical symptoms and demography of confirmed cases were analyzed.

Results

A total of 480 scrub typhus cases were confirmed. The cases occurred every year exclusively between September and December with a peak occurrence in October. The case numbers were relatively higher in 1995, 1996, 1997, and 2000 than in other years. 57.9% of cases were in the group aged 21–50. More cases occurred in male (56%) than in female (44%). The predominant occupational group of the cases was farmers (85.0%). Farm work was reported the primary exposure to infection in 67.7% of cases. Fever, rash, and eschar were observed in 100.0%, 90.4%, and 88.5% of cases, respectively. Eschars formed frequently on or around umbilicus, abdomen areas, and front and back of waist (34.1%) in both genders. Normal results were observed in 88.7% (WBC counts), 84.5% (PLT counts), and 89.7% (RBC counts) of cases, respectively. Observations from the five hospitals were compared and no significant differences were found.

Conclusion

The autumn-winter type scrub typhus in northern China occurred exclusively from September to December with a peak occurrence in October, which was different from the summer type in southern China. In comparison with the summer type, complications associated with autumn-winter type scrub typhus were less severe, and abnormalities of routine hematological parameters were less obvious.