title: Geographic and temporal trends in influenzalike illness, Japan, 1992-1999.
abstract: From 1992 to 1999, we analyzed >2.5 million cases of influenzalike illness (ILI). Nationwide influenza epidemics generally lasted 3-4 months in winter. Kriging analysis, which illustrates geographic movement, showed that the starting areas of peak ILI activity were mostly found in western Japan. Two spreading patterns, monotonous and multitonous, were observed. Monotonous patterns in two seasons featured peak ILI activity that covered all of Japan within 3 to 5 weeks in larger epidemics with new antigenic variants of A/H3N2. Multitonous patterns, observed in the other five seasons, featured peak ILI activity within 12 to 15 weeks in small epidemics without new variants. Applying the kriging method allowed better visualization and understanding of spatiotemporal trends in seasonal ILI activity. This method will likely be an important tool for future influenza surveillance in Japan.
authors.affiliation: Department of Public Health, Niigata University School of Medicine, Niigata 951-8510, Japan. tsakai@med.niigata-u.ac.jp
authors.forename: Takatsugu
authors.initials: T
authors.lastname: Sakai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Asami
authors.initials: A
authors.lastname: Sasaki
authors.forename: Reiko
authors.initials: R
authors.lastname: Saito
authors.forename: Naohito
authors.initials: N
authors.lastname: Tanabe
authors.forename: Kiyosu
authors.initials: K
authors.lastname: Taniguchi
mesh_terms: D004196:Disease Outbreaks; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D007564:Japan / Q000453:epidemiology; D011159:Population Surveillance / Q000379:methods; D012044:Regression Analysis; D012621:Seasons; D013223:Statistics as Topic / Q000379:methods