Evaluation of FluSight influenza forecasting in the 2021-22 and 2022-23 seasons with a new target laboratory-confirmed influenza hospitalizations
Authors: Mathis Sarabeth M. , Webber Alexander E. , León Tomás M. , Murray Erin L. , Sun Monica , White Lauren A. , Brooks Logan C. , Green Alden , Hu Addison J. , McDonald Daniel J. , Rosenfeld Roni , Shemetov Dmitry , Tibshirani Ryan J. , Kandula Sasikiran , Pei Sen , Shaman Jeffrey , Yaari Rami , Yamana Teresa K. , Agarwal Pulak , Balusu Srikar , Gururajan Gautham , Kamarthi Harshavardhan , Prakash B. Aditya , Raman Rishi , Rodríguez Alexander , Zhao Zhiyuan , Meiyappan Akilan , Omar Shalina , Baccam Prasith , Gurung Heidi L. , Stage Steve A. , Suchoski Brad T. , Ajelli Marco , Kummer Allisandra G. , Litvinova Maria , Ventura Paulo C. , Wadsworth Spencer , Niemi Jarad , Carcelen Erica , Hill Alison L , Jung Sung-mok , Lemaitre Joseph C. , Lessler Justin , Loo Sara L , McKee Clifton D. , Sato Koji , Smith Claire , Truelove Shaun , McAndrew Thomas , Ye Wenxuan , Bosse Nikos , Hlavacek William S. , Lin Yen Ting , Mallela Abhishek , Chen Ye , Lamm Shelby M. , Lee Jaechoul , Posner Richard G. , Perofsky Amanda C. , Viboud Cécile , Clemente Leonardo , Lu Fred , Meyer Austin G , Santillana Mauricio , Chinazzi Matteo , Davis Jessica T. , Mu Kunpeng , Pastore y Piontti Ana , Vespignani Alessandro , Xiong Xinyue , Ben-Nun Michal , Riley Pete , Turtle James , Hulme-Lowe Chis , Jessa Shakeel , Nagraj V.P. , Turner Stephen D. , Williams Desiree , Basu Avranil , Drake John M. , Fox Spencer J. , Gibson Graham C. , Suez Ehsan , Thommes Edward W. , Cojocaru Monica G. , Cramer Estee Y. , Gerding Aaron , Stark Ariane , Ray Evan L. , Reich Nicholas G. , Shandross Li , Wattanachit Nutcha , Wang Yijin , Zorn Martha W. , Aawar Majd Al , Srivastava Ajitesh , Meyers Lauren A. , Adiga Aniruddha , Hurt Benjamin , Kaur Gursharn , Lewis Bryan L. , Marathe Madhav , Venkatramanan Srinivasan , Butler Patrick , Farabow Andrew , Muralidhar Nikhil , Ramakrishnan Naren , Reed Carrie , Biggerstaff Matthew , Borchering Rebecca K. 
Published: December 2023

Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. Forecasting teams were asked to provide national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one through four weeks ahead for the 2021-22 and 2022-23 influenza seasons.

Across both seasons, 26 teams submitted forecasts, with the submitting teams varying between seasons. Forecast skill was evaluated using the Weighted Interval Score (WIS), relative WIS, and coverage.

Six out of 23 models outperformed the baseline model across forecast weeks and locations in 2021-22 and 12 out of 18 models in 2022-23. Averaging across all forecast targets, the FluSight ensemble was the 2ndmost accurate model measured by WIS in 2021-22 and the 5thmost accurate in the 2022-23 season. Forecast skill and 95% coverage for the FluSight ensemble and most component models degraded over longer forecast horizons and during periods of rapid change.

Current influenza forecasting efforts help inform situational awareness, but research is needed to address limitations, including decreased performance during periods of changing epidemic dynamics.