Abstract
Background: Few reports have longitudinally investigated seasonal influenza epidemiological surveillance data of pediatric populations in the metropolitan areas of Japan. We aimed to provide descriptive characteristics of circulating influenza and to investigate the usefulness of setting thresholds for influenza in children (0–15 years old) in two satellite cities of a metropolitan area of Tokyo, Japan, for five consecutive seasons of the influenza epidemic.Methods: The survey was conducted annually during the influenza season, from 2014 to 2018 (ending March 2019), at preschools (kindergartens and nursery schools), elementary schools, and junior high schools located in Toda and Warabi cities, Saitama prefecture. We investigated the epidemiological characteristics and established thresholds using the World Health Organization method.Results: Of the 108,362 children (21,024 to 22,088 throughout five seasons) who received the questionnaire, 76,753 (70.8%; 14,652 to 15,808) responded. After exclusion of responses without basic information, 64,586 children were included in the analysis, of which 13,754 (21.3%) had tested positive for influenza. Influenza type A was generally dominant, whereas type B was responsible for a substantial share of all influenza cases (>40% in seasons 2015 and 2017, when type A circulated with low incidence). The weeks when the influenza epidemic peaked had no clear seasonal pattern among the surveyed years, i.e., the peaks appeared at week 51 (mid-December) or later, whereas the World Health Organization methods reported that the median period when a peak was observed was at 3 weeks (mid-January), regardless of school age group.Conclusions: The present information obtained from the epidemiological survey regarding seasonal influenza in children would be useful for general practitioners, health policymakers, and planners who establish prevention and control methods against influenza.
COVID-19 border controls prevent a 2021 seasonal influenza epidemic in New Zealand
