title: Concurrent epidemics of influenza A/H3N2 and A/H1N1pdm in Southern China: A serial cross-sectional study.
abstract: OBJECTIVE
  This study aimed to elucidate the antibody response pattern of multiple influenza subtypes through a 4-year serological study of a general population in Shenzhen, Southern China.
  
  
  METHODS
  A serial cross-sectional serological survey was conducted at eight time points between 2009 and 2012. A total number of 5876 subjects were recruited from all age groups. The influenza subtypes tested were A/H1N1, A/H3N2, B/Yamagata, B/Victoria, and A/H1N1pdm. Genetic sequencing and phylogenetic analysis were performed on 127 H3 genes and 28 H1pdm genes.
  
  
  RESULTS
  We found concurrent epidemics of A/H3N2 and A/H1N1pdm with simultaneous peak times at March 2011. A/H3N2 was the dominant subtype. Ten residue substitutions (S61N, T64I, K78E, K160N, N161S, A214S, T228A, A229V, V239I, N294K, and N328S) were found in the H3 gene that might underlie its epidemic. The elderly group showed an antibody response cycle that was weaker in magnitude and slower in peak time than in younger groups.
  
  
  CONCLUSIONS
  The study provides a broad transmission picture and epidemiological characteristics of the major flu subtypes. The findings suggest that it may be necessary to include the A/H1N1pdm strain to the current trivalent or quadrivalent vaccine design. The delayed antibody response cycle in the elderly group indicates the need for better protection of elderly people that might be achieved by an earlier vaccination at a higher dose.
authors.affiliation: Major Infectious Disease Control Key Laboratory, The Shenzhen Center for Disease Control and Prevention, Shenzhen, China.
authors.forename: Chunli
authors.initials: C
authors.lastname: Wu
authors.affiliation: Division of Biostatistics, JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong SAR, China; The CUHK Shenzhen Research Institute, Shenzhen, China.
authors.forename: Maggie Haitian
authors.initials: MH
authors.lastname: Wang
authors.affiliation: Major Infectious Disease Control Key Laboratory, The Shenzhen Center for Disease Control and Prevention, Shenzhen, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.affiliation: Division of Biostatistics, JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong SAR, China; The CUHK Shenzhen Research Institute, Shenzhen, China.
authors.forename: Ka Chun
authors.initials: KC
authors.lastname: Chong
authors.affiliation: College of Letter and Science, University of California at Berkeley, CA, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Statistics, The Chinese University of Hong Kong, Hong Kong SAR, China.
authors.forename: Chun-Yip
authors.initials: CY
authors.lastname: Yau
authors.affiliation: Department of Statistics, The Chinese University of Hong Kong, Hong Kong SAR, China.
authors.forename: Mark
authors.initials: M
authors.lastname: Hui
authors.affiliation: Major Infectious Disease Control Key Laboratory, The Shenzhen Center for Disease Control and Prevention, Shenzhen, China.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Division of Digestive Diseases, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.affiliation: Division of Biostatistics, JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong SAR, China; The CUHK Shenzhen Research Institute, Shenzhen, China.
authors.forename: Benny Chung-Ying
authors.initials: BC
authors.lastname: Zee
authors.affiliation: Major Infectious Disease Control Key Laboratory, The Shenzhen Center for Disease Control and Prevention, Shenzhen, China. Electronic address: renlizhang@tom.com.
authors.forename: Renli
authors.initials: R
authors.lastname: Zhang
authors.affiliation: The CUHK Shenzhen Research Institute, Shenzhen, China; Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, China; Department of Biomedical Science, The City University of Hong Kong, Hong Kong SAR, China. Electronic address: mlhe7788@gmail.com.
authors.forename: Ming-Liang
authors.initials: ML
authors.lastname: He
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D058872:Epidemics; D005260:Female; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus
keywords: Antibody response; Concurrent epidemics; Elderly; H1N1pdm; H3N2; Influenza