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A Large-Scale Community-Based Outbreak of Paratyphoid Fever Caused by Hospital-Derived Transmission in Southern China

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      Abstract

      BackgroundSince the 1990s, paratyphoid fever caused by Salmonella Paratyphi A has emerged in Southeast Asia and China. In 2010, a large-scale outbreak involving 601 cases of paratyphoid fever occurred in the whole of Yuanjiang county in China. Epidemiological and laboratory investigations were conducted to determine the etiology, source and transmission factors of the outbreak.Methodology/Principal FindingsA case-control study was performed to identify the risk factors for this paratyphoid outbreak. Cases were identified as patients with blood culture–confirmed S. Paratyphi A infection. Controls were healthy persons without fever within the past month and matched to cases by age, gender and geography. Pulsed-field gel electrophoresis and whole-genome sequencing of the S. Paratyphi A strains isolated from patients and environmental sources were performed to facilitate transmission analysis and source tracking. We found that farmers and young adults were the populations mainly affected in this outbreak, and the consumption of raw vegetables was the main risk factor associated with paratyphoid fever. Molecular subtyping and genome sequencing of S. Paratyphi A isolates recovered from improperly disinfected hospital wastewater showed indistinguishable patterns matching most of the isolates from the cases. An investigation showed that hospital wastewater mixed with surface water was used for crop irrigation, promoting a cycle of contamination. After prohibition of the planting of vegetables in contaminated fields and the thorough disinfection of hospital wastewater, the outbreak subsided. Further analysis of the isolates indicated that the origin of the outbreak was most likely from patients outside Yuanjiang county.ConclusionsThis outbreak is an example of the combined effect of social behaviors, prevailing ecological conditions and improper disinfection of hospital wastewater on facilitating a sustained epidemic of paratyphoid fever. This study underscores the critical need for strict treatment measures of hospital wastewater and the maintenance of independent agricultural irrigation systems in rural areas.

      Author Summary

      Typhoid and paratyphoid fever remain public health concerns for developing countries. From May 2010 to June 2011, a large-scale outbreak involving 601 cases of paratyphoid fever occurred in China. Epidemiological and laboratory investigations were conducted to determine the etiology, source and transmission factors of the outbreak. Farmers and young adults were the populations mainly affected in this outbreak, and the consumption of raw vegetables was the main risk factor associated with paratyphoid fever. We found that hospital wastewater mixed with surface water was used for vegetable irrigation. The contaminated water from hospitals combined with the regional habit of eating uncooked vegetables lead to the massive outbreak of paratyphoid. After prohibition of the planting of vegetables in contaminated fields and the thorough disinfection of hospital wastewater, the outbreak subsided. Molecular subtyping and whole-genome sequencing of S. Paratyphi A isolates recovered from improperly disinfected hospital wastewater showed indistinguishable patterns matching most of the isolates from the cases. Further analysis of the isolates indicated that the origin of the outbreak was most likely from patients outside Yuanjiang county. This study underscores the critical need for strict treatment measures of hospital wastewater and the maintenance of independent agricultural irrigation systems in rural areas.

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      Most cited references 25

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            Author and article information

            Affiliations
            [1 ]State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
            [2 ]Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, Zhejiang, China
            [3 ]Center for Disease Control and Prevention of Yuanjiang County, Yunnan, China
            [4 ]Center for Disease Control and Prevention of Yuxi City, Yunnan, China
            [5 ]International Emerging Infections Program, US Centers for Disease Control and Prevention, Beijing, China
            [6 ]Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
            Massachusetts General Hospital, UNITED STATES
            Author notes

            The authors have declared that no competing interests exist.

            Conceived and designed the experiments: BK MY BY ZW SWa. Performed the experiments: MY BY XZ YZ BD RY. Analyzed the data: BK MY BY SWu JDK BP. Wrote the paper: BK MY SWu JDK.

            Contributors
            Role: Editor
            Journal
            PLoS Negl Trop Dis
            PLoS Negl Trop Dis
            plos
            plosntds
            PLoS Neglected Tropical Diseases
            Public Library of Science (San Francisco, CA USA )
            1935-2727
            1935-2735
            17 July 2015
            July 2015
            : 9
            : 7
            26186586
            4506061
            10.1371/journal.pntd.0003859
            PNTD-D-14-02058
            (Editor)

            This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication

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            Figures: 4, Tables: 1, Pages: 14
            Product
            Funding
            This work was supported by the Priority Project on Infectious Disease Control and Prevention [BK grant numbers 2012ZX10004215, 2008ZX10004-008] from the Ministry of Science and Technology of the People's Republic of China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
            Categories
            Research Article
            Custom metadata
            All relevant data are within the paper and its Supporting Information files.

            Infectious disease & Microbiology

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