title: Epidemiologic features and environmental risk factors of severe fever with thrombocytopenia syndrome, Xinyang, China.
abstract: BACKGROUND
  Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease discovered in rural areas of Central China in 2009, caused by a novel bunyavirus, SFTS virus (SFTSV). The disease usually presents as fever, thrombocytopenia, and leukocytopenia, with case-fatality rates ranging from 2.5% to 30%. Haemaphysalis longicornis was suspected to be the most likely vector of SFTSV. By the end of 2012, the disease had expanded to 13 provinces of China. SFTS patients have been reported in Japan and South Korea, and a disease similar to SFTS has been reported in the United States.
  
  
  RESULTS
  We characterized the epidemiologic features of 504 confirmed SFTS cases in Xinyang Region, the most severely SFTS-afflicted region in China from 2011 to 2012, and assessed the environmental risk factors. All cases occurred during March to November, with the epidemic peaking from May to July. The patients' ages ranged from 7 to 87 years (median 61 years), and the annual incidence increased with age (χ2 test for trend, P<0.001). The female-to-male ratio of cases was 1.58, and 97.0% of the cases were farmers who resided in the southern and western parts of the region. The Poisson regression analysis revealed that the spatial variations of SFTS incidence were significantly associated with the shrub, forest, and rain-fed cropland areas.
  
  
  CONCLUSIONS
  The distribution of SFTS showed highly significant temporal and spatial heterogeneity in Xinyang Region, with the majority of SFTS cases being elderly farmers who resided in the southern and western parts of the region, mostly acquiring infection between May and July when H. longicornis is highly active. The shrub, rain-fed, and rain-fed cropland areas were associated with high risk for this disease.
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: The 154 Hospital, People's Liberation Army, Xinyang, People's Republic of China.
authors.forename: Ning
authors.initials: N
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Fang
authors.affiliation: The 154 Hospital, People's Liberation Army, Xinyang, People's Republic of China.
authors.forename: Bing-Jun
authors.initials: BJ
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Qing-Bin
authors.initials: QB
authors.lastname: Lu
authors.affiliation: The Shangcheng People's Hospital, Shangcheng, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China; Anhui Medical University, Hefei, People's Republic of China.
authors.forename: Li-Yuan
authors.initials: LY
authors.lastname: Wang
authors.affiliation: Environmental and Global Health, College of Public Health and Health Professions, and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Song
authors.initials: S
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China; Anhui Medical University, Hefei, People's Republic of China.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China; Anhui Medical University, Hefei, People's Republic of China.
authors.forename: Yao-Yun
authors.initials: YY
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhuang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.affiliation: Environmental and Global Health, College of Public Health and Health Professions, and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Gray
authors.affiliation: Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Sake J
authors.initials: SJ
authors.lastname: de Vlas
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, People's Republic of China.
authors.forename: Wu-Chun
authors.initials: WC
authors.lastname: Cao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000383:Agriculture; D002044:Bunyaviridae Infections / Q000453:epidemiology* / Q000821:virology; D002648:Child; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016856:Phlebovirus / Q000302:isolation & purification*; D016012:Poisson Distribution; D012307:Risk Factors; D012621:Seasons; D055815:Young Adult