Nowcasting (Short-Term Forecasting) of Influenza Epidemics in Local Settings, Sweden, 2008-2019.

Armin Spreco,Olle Eriksson,Emanuel Istefan,Anna Jöud,Matthew Biggerstaff,Benjamin John Cowling,Gunnar Ljunggren,Örjan Dahlström,Toomas Timpka

doi:10.3201/eid2611.200448

Abstract

The timing of influenza case incidence during epidemics can differ between regions within nations and states. We conducted a prospective 10-year evaluation (January 2008–February 2019) of a local influenza nowcasting (short-term forecasting) method in 3 urban counties in Sweden with independent public health administrations by using routine health information system data. Detection-of-epidemic-start (detection), peak timing, and peak intensity were nowcasted. Detection displayed satisfactory performance in 2 of the 3 counties for all nonpandemic influenza seasons and in 6 of 9 seasons for the third county. Peak-timing prediction showed satisfactory performance from the influenza season 2011–12 onward. Peak-intensity prediction also was satisfactory for influenza seasons in 2 of the counties but poor in 1 county. Local influenza nowcasting was satisfactory for seasonal influenza in 2 of 3 counties. The less satisfactory performance in 1 of the study counties might be attributable to population mixing with a neighboring metropolitan area.

Highlights

The timing of influenza case incidence during epidemics can differ between regions within nations and states
We describe a prospective 10-year evaluation of this local influenza nowcasting method in 3 urban counties in Sweden
The clinical influenza case data were used to detect the local start of the epidemic and prediction of its peak intensity, and the syndromic data were used to predict the peak timing

Summary

Introduction

The timing of influenza case incidence during epidemics can differ between regions within nations and states. We conducted a prospective 10-year evaluation (January 2008–February 2019) of a local influenza nowcasting (short-term forecasting) method in 3 urban counties in Sweden with independent public health administrations by using routine health information system data. Modelers have shown considerable interest in developing infectious disease forecasts, the readiness in the public health community for applying these predictions has been lacking [3] One reason for this discrepancy might be that national public health policies for response to infectious disease outbreaks often assign the responsibility for healthcare resource allocation to local health authorities (i.e., county and municipality governments). A need exists for influenza forecasting methods that harmonize with policy-making responsibilities at local government levels and that are more relevant for public health practitioners Another reason for the poor uptake of forecasting methods might be a lack of prospective evaluations of their reliability. The appraisal concluded that a longer prospective evaluation was needed to ascertain the validity of the results and that data from larger urban counties were required to draw reliable conclusions about generalizability

Methods

Results

Conclusion