Researchers say that hospitalization rates among older adults peaked several weeks earlier than children in the 2017-18 flu season compared with previous years.

During the 2017-2018 season, hospitalization rates in adults aged 65 years and older peaked 3 weeks before they peaked in children aged 0 to 4 years. According to Garg and colleagues, during the four prior seasons, rates in adults peaked the same week or 1 week after they peaked in children.

Additionally, during the 2017-2018 season, the distribution of influenza types or subtypes varied significantly by age group. For example, the authors said, the proportion of patients with H1N1 ranged from 19% to 29% in those younger than age 65 years to only 7% in those aged 65 years and older.