title: Shifting seroepidemiology of hepatitis A in Japan, 1973-2003.
abstract: BACKGROUND
  Hepatitis A infection is caused by hepatitis A virus (HAV) contracted through fecal-oral transmission. Life-long immunity is conferred after infection. Improved sanitary conditions have generally resulted in a significant decline in the incidence of hepatitis A. However, a low incidence of infection results in increased HAV susceptibility. The present study investigates the prevalence of anti-HAV antibody and clarifies the current HAV status and HAV susceptibility in Japan at 2003.
  
  
  METHODS
  A total of 2,430 serum specimens collected during 2003 from Japanese individuals ranging in age from 0-92 years, were tested for anti-HAV antibody using an inhibition enzyme linked immunosorbent assay. All specimens were obtained from the WHO and the National Serum Reference Bank/National Institute of Infectious Diseases, Tokyo, Japan.
  
  
  RESULTS
  The overall seroprevalence was 12.2%. Anti-HAV antibodies were rarely detected in individuals between 0-44 years of age. Starting from the age of 45-49 years, seropositivity gradually increased through age 65 years and above. Seroprevalence was not affected by gender, and geographic distribution did not affect age-specific seroprevalence until the age of 60 years.
  
  
  CONCLUSIONS
  HAV susceptibility in Japan is increasing annually. Particularly, the prevalence of anti-HAV antibody in individuals older than 50 years in 2003 was 50.3%, which is significantly lower than that of corresponding studies in 1994 (74.3%), 1984 (96.9%) and 1973 (96.9%). The growing susceptible population of advanced age results in more frequent HAV infection among them. The surveillance of anti-HAV antibody prevalence is useful for implementing preventive measures and for controlling the spread of HAV.
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Musashi-murayama, Tokyo, Japan. kiyohara@nih.go.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kiyohara
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sato
authors.forename: Atsuko
authors.initials: A
authors.lastname: Totsuka
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Miyamura
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ito
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yoneyama
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology* / Q000821:virology; D035922:Hepatitis A Antibodies / Q000097:blood; D017957:Hepatitis A Virus, Human / Q000302:isolation & purification*; D006801:Humans; D007223:Infant; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016036:Seroepidemiologic Studies
chemical_list: D035922:Hepatitis A Antibodies