title: Evaluation of inapparent dengue infections during an outbreak in Southern China.
abstract: Few studies evaluating inapparent dengue virus (DENV) infections have been conducted in China. In 2013, a large outbreak of DENV occurred in the city of Zhongshan, located in Southern China, which provided an opportunity to assess the clinical spectrum of disease. During the outbreak, an investigation of 887 index case contacts was conducted to evaluate inapparent and symptomatic DENV infections. Post-outbreak, an additional 815 subjects from 4 towns with, and 350 subjects from 2 towns without reported autochthonous DENV transmission, as determined by clinical diagnosis, were evaluated for serological evidence of dengue IgG antibodies. Between July and November 2013, there were 19 imported and 809 autochthonous dengue cases reported in Zhongshan. Of 887 case contacts enrolled during the outbreak, 13 (1.5%) exhibited symptomatic DENV infection, while 28 (3.2%) were inapparent. The overall I:S ratio was 2.2:1 (95% CI: 1.1-4.2:1). Post-outbreak serological data showed that the proportion of DENV IgG antibody detection from the 4 towns with and the 2 towns without reported DENV transmission was 2.7% (95% CI: 1.6%-3.8%) and 0.6% (95% CI: 0-1.4%), respectively. The I:S ratio in the 3 towns where clinical dengue cases were predominately typed as DENV-1 was 11.0:1 (95% CI: 3.7-∞:1). The ratio in the town where DENV-3 was predominately typed was 1.0:1 (95% CI: 0.5-∞:1). In this cross-sectional study, data suggests a high I:S ratio during a documented outbreak in Zhongshan, Southern China. These results have important implications for dengue control, implying that inapparent cases might influence DENV transmission more than previously thought.
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China; Zhongshan Institute of the School of Public Health, Sun Yat-sen University, Zhongshan, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Man
authors.initials: M
authors.lastname: Wang
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Shu
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Xue-qin
authors.initials: XQ
authors.lastname: Chen
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Le
authors.initials: L
authors.lastname: Luo
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Jin-yu
authors.initials: JY
authors.lastname: Wang
authors.affiliation: Zhongshan Center for Disease Control and Prevention, Zhongshan, China.
authors.forename: Yong-zhuang
authors.initials: YZ
authors.lastname: Cen
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Duke University, Durham, North Carolina, United States of America.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Anderson
authors.affiliation: Department of Environmental & Global Health, College of Public Health & Health Professions, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Mary M
authors.initials: MM
authors.lastname: Merrill
authors.affiliation: Department of Statistics, College of Liberal Arts & Sciences, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Hunter R
authors.initials: HR
authors.lastname: Merrill
authors.affiliation: Zhongshan Institute of the School of Public Health, Sun Yat-sen University, Zhongshan, China; School of Public Health, Sun Yat-sen University, Guangzhou, China.
authors.forename: Jia-hai
authors.initials: JH
authors.lastname: Lu
mesh_terms: D058345:Asymptomatic Infections / Q000453:epidemiology*; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003715:Dengue / Q000453:epidemiology* / Q000473:pathology / Q000635:transmission*; D003716:Dengue Virus / Q000276:immunology*; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood
chemical_list: D007074:Immunoglobulin G
references.citation: Emerg Infect Dis. 1999 Nov-Dec;5(6):824-7
references.pmid: 10603220
references.citation: Trop Med Int Health. 2002 Apr;7(4):331-8
references.pmid: 11952949
references.citation: Am J Epidemiol. 2002 Jul 1;156(1):40-51
references.pmid: 12076887
references.citation: Zhonghua Liu Xing Bing Xue Za Zhi. 2002 Dec;23(6):427-30
references.pmid: 12667352
references.citation: Zhonghua Liu Xing Bing Xue Za Zhi. 2003 Apr;24(4):288-90
references.pmid: 12820947
references.citation: Am J Trop Med Hyg. 2005 Jan;72(1):60-6
references.pmid: 15728868
references.citation: Am J Trop Med Hyg. 2005 Jun;72(6):777-82
references.pmid: 15967759
references.citation: PLoS Med. 2008 Nov 4;5(11):e205
references.pmid: 18986209
references.citation: Curr Top Microbiol Immunol. 2010;338:1-13
references.pmid: 19802574
references.citation: J Infect Dis. 2010 Jan 1;201(1):5-14
references.pmid: 19929380
references.citation: Am J Trop Med Hyg. 2010 Sep;83(3):664-71
references.pmid: 20810836
references.citation: Am J Trop Med Hyg. 2010 Sep;83(3):683-9
references.pmid: 20810839
references.citation: PLoS Negl Trop Dis. 2011 Mar 01;5(3):e975
references.pmid: 21390158
references.citation: Emerg Infect Dis. 2011 May;17(5):821-8
references.pmid: 21529390
references.citation: BMC Public Health. 2012 Jan 24;12:72
references.pmid: 22272602
references.citation: Transfusion. 2012 Aug;52(8):1657-66
references.pmid: 22339201
references.citation: Front Physiol. 2012 Mar 30;3:70
references.pmid: 22479252
references.citation: J Infect Dis. 2012 Aug 1;206(3):389-98
references.pmid: 22615312
references.citation: Transfusion. 2012 Aug;52(8):1634-9
references.pmid: 22882092
references.citation: Viral Immunol. 2012 Dec;25(6):456-60
references.pmid: 23216307
references.citation: Virol J. 2013 Jan 02;10:4
references.pmid: 23282129
references.citation: Nature. 2013 Apr 25;496(7446):504-7
references.pmid: 23563266
references.citation: Emerg Infect Dis. 2013 May;19(5):787-9
references.pmid: 23648012
references.citation: Am J Trop Med Hyg. 1988 Jan;38(1):172-80
references.pmid: 3341519
references.citation: Am J Trop Med Hyg. 1981 Sep;30(5):1094-9
references.pmid: 7283006
references.citation: Am J Trop Med Hyg. 1996 Jul;55(1):12-6
references.pmid: 8702015