title: Number of sentinel medical institutions needed for estimating prefectural incidence in influenza surveillance in Japan.
abstract: BACKGROUND
  The sentinel surveillance system in Japan provides estimates of nationwide influenza incidence. Although prefectural influenza incidences can be estimated using data from the current surveillance system, such estimates may be imprecise.
  
  
  METHODS
  We calculated the numbers of sentinel medical institutions (SMIs) needed in the surveillance system to estimate influenza incidences in prefectures, under the assumption that the standard error rates in 75% of influenza epidemic cases are less than 10%. Epidemic cases observed in 47 prefectures during the 2007/2008, 2008/2009, and 2009/2010 seasons, respectively, were used.
  
  
  RESULTS
  The present total number of SMIs was 6669. With respect to current standards, the increases required in prefectures ranged from 0 to 59, and the total increase required in the number of SMIs was 1668.
  
  
  CONCLUSIONS
  We used sentinel surveillance data for Japan to calculate the number of SMIs required to estimate influenza incidence in each prefecture.
authors.affiliation: Department of Hygiene, Fujita Health University School of Medicine.
authors.forename: Shuji
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kawado
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Murakami
authors.forename: Akiko
authors.initials: A
authors.lastname: Ohta
authors.forename: Mika
authors.initials: M
authors.lastname: Shigematsu
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tada
authors.forename: Kiyosu
authors.initials: K
authors.lastname: Taniguchi
authors.forename: Masaki
authors.initials: M
authors.lastname: Nagai
mesh_terms: D058872:Epidemics / Q000706:statistics & numerical data*; D006268:Health Facilities / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007251:Influenza, Human / Q000453:epidemiology*; D007564:Japan / Q000453:epidemiology; D020380:Needs Assessment; D015203:Reproducibility of Results; D012621:Seasons; D018571:Sentinel Surveillance