Predicting Influenza Outbreak in One Nursery and in the Community Using the Nursery and School Absenteeism Surveillance System

Abstract

Since 2013, all nurseries and elementary/junior high schools (schools hereinafter) in Sumida ward, Tokyo participate in the Nursery and School Absenteeism Surveillance System (NaSASSy). Nurseries and schools report the number of absentees in each class by diagnosis and by symptom every business day via the web system. We predicted the date of seasonal influenza outbreak in a nursey using real-time data of influenza in nurseries and schools in Sumida ward directly accessible from NaSASSy, which would allow the nursery to plan preventive measures. Outbreak was defined as occurrence of the second case in a school or nursery. Incidence rates and epidemic curves of influenza for Nursery H (150 children in 2013) were compared with those for all nurseries (4,460 children) and all schools in Sumida during four seasons (2013/2014 to 2016/2017). In three seasons, the initial case in Nursery H occurred at a minimum of 41 days and a maximum of 89 days after detection of the second case in schools. In four seasons, the initial case in Nursery H occurred at a minimum of 21 days after detection of the second case in all nurseries. Season with high incidence rate alternated with season with low rate. In seasons when Nursery H had high incidence rates, the 5-year-old class always had high rates. In conclusion, real-time detection of influenza outbreak in the community by NaSASSy and using the second case in schools as an indicator of outbreak is useful for nurseries to predict the coming outbreak and plan preventive measures.

Keywords

• nursery and school absenteeism surveillance systems (nasassy)
• outbreak
• infection
• surveillance
• influenza