title: Epidemiological information regarding the periodic epidemics of influenza C virus in Japan (1996-2013) and the seroprevalence of antibodies to different antigenic groups.
abstract: BACKGROUND
  Although influenza C virus is widely distributed throughout the world, epidemiological information, based on long-term surveillance, has not yet been acquired.
  
  
  OBJECTIVE
  To clarify the epidemiological features of influenza C virus infection, and to examine whether the prevalence of the antibodies against the influenza C virus is associated with the epidemics.
  
  
  METHODS
  Between 1996 and 2013, 36,973 respiratory specimens were collected from two pediatric outpatient clinics in Yamagata, Japan. The specimens were examined for the presence of influenza C virus using cell culture methods. Isolated viruses were antigenically analyzed. The differences in seropositivity, with respect to the different antigenic groups, were examined using serum samples collected in 2001 and 2011 by a hemagglutination inhibition assay.
  
  
  RESULTS
  Influenza C viruses were isolated from 190 specimens during an 18-year period. Most influenza C viruses were isolated from winter to early summer in even-numbered years, and the frequency of virus isolation per year ranged from 0.43% to 1.73%. An antigenic analysis revealed that the dominant antigenic groups were the C/Yamagata/26/81 from 1996 to 2000, the C/Kanagawa/1/76 in 2002 and 2004, and the C/Sao Paulo/378/82 from 2006 to 2012. When compared to the other antigenic groups, the seroprevalence of the C/Sao Paulo/378/82 group was lower in 2001 for individuals older than 5 years and was higher in 2011 in individuals younger than 40 years.
  
  
  CONCLUSIONS
  The results from our study suggest that epidemics of influenza C virus infection periodically occur and the replacement of the dominant antigenic group may be caused by immune selection within older children and/or adults in the community.
authors.affiliation: Department of Infectious Diseases, Yamagata University Faculty of Medicine, Iida-Nishi, Yamagata 990-9585, Japan. Electronic address: matuzaki@med.id.yamagata-u.ac.jp.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Matsuzaki
authors.affiliation: Department of Infectious Diseases, Yamagata University Faculty of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
authors.forename: Kanetsu
authors.initials: K
authors.lastname: Sugawara
authors.affiliation: Department of Microbiology, Yamagata Prefectural Institute of Public Health, Tokamachi, Yamagata 990-0031, Japan.
authors.forename: Chieko
authors.initials: C
authors.lastname: Abiko
authors.affiliation: Department of Microbiology, Yamagata Prefectural Institute of Public Health, Tokamachi, Yamagata 990-0031, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Department of Microbiology, Yamagata Prefectural Institute of Public Health, Tokamachi, Yamagata 990-0031, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Department of Microbiology, Yamagata Prefectural Institute of Public Health, Tokamachi, Yamagata 990-0031, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Mizuta
authors.affiliation: Katsushima Pediatric Clinic, Minamidate, Yamagata 990-2461, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Katsushima
authors.affiliation: Katsushima Pediatric Clinic, Minamidate, Yamagata 990-2461, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Katsushima
authors.affiliation: Katsushima Pediatric Clinic, Minamidate, Yamagata 990-2461, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Katsushima
authors.affiliation: Yamanobe Pediatric Clinic, Yamanobe, Yamagata 990-0301, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Itagaki
authors.affiliation: Department of Infectious Diseases, Yamagata University Faculty of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Shimotai
authors.affiliation: Department of Infectious Diseases, Yamagata University Faculty of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Hongo
authors.affiliation: Department of Infectious Diseases, Yamagata University Faculty of Medicine, Iida-Nishi, Yamagata 990-9585, Japan; Department of Microbiology, Kanazawa Medical University School of Medicine, Uchinada, Ishikawa 920-0293, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Muraki
authors.affiliation: Virus Research Center, Clinical Research Division, Sendai Medical Center, Miyagino-ku, Sendai, Miyagi 983-8520, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Nishimura
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D058872:Epidemics; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D009982:Gammainfluenzavirus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D014776:Virus Cultivation; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D012367:RNA, Viral
keywords: Antigenic drift; Influenza C virus; Seroprevalence; Surveillance