Week 1 Influenza Forecast for the 2012-2013 U.S. Season

TL;DR

This paper presents weekly influenza forecasts for the 2012-2013 U.S. season, analyzing initial predictions, their accuracy, and adjustments made to improve future forecasts amid season-specific challenges.

Contribution

It introduces a method for adjusting influenza forecasts based on observed virulence and ILI levels to improve accuracy during an atypical flu season.

Findings

Initial forecasts showed inaccuracies likely due to high virulence

Adjusted forecasts better matched early peak cities

Forecasts for subsequent weeks are being refined

Abstract

This is part of a series of weekly influenza forecasts made during the 2012-2013 influenza season. Here we present results of forecasts initiated following assimilation of observations for Week 1 (i.e. the forecast begins January 6, 2013) for municipalities in the United States. These forecasts were performed on January 11, 2013. Results from forecasts initiated the six previous weeks (Weeks 47-52) are also presented. The accuracy of these predictions will not be known for certain until the conclusion of the current influenza season; however, at the moment a number of the forecasted peaks appear to be inaccurate. This inaccuracy may be due to the virulence of influenza this season, which appears to be sending more influenza-infected persons to seek medical attention and inflates ILI levels (and possibly the proportion testing influenza positive) relative to years with milder flu strains. New forecasts that adjust, or scale, for this difference and match the two focus cities that appear to have already peaked are identified. These new forecasts will be used, in addition to the previously scaled forms, to make influenza predictions for the remainder of the season.