The 2017-2018 influenza season was a high severity season with high levels of outpatient clinic and emergency department visits for influenza-like illness (ILI), high influenza-related hospitalization rates, and elevated and geographically widespread influenza activity for an extended period. In 2017, CDC began using new methodology(https://www.cdc.gov/flu/professionals/classifies-flu-severity.htm) to classify seasonal severity and applied the methodology to the 2003-2004 through 2016-2017 seasons. The 2017-18 season was the first season to be classified as a high severity across all age groups.