During the 2017-2018 season, the percentage of deaths attributed to pneumonia and influenza was at or above the epidemic threshold for 16 consecutive weeks. During the past five seasons, the average number of weeks this indicator was above threshold was 11 (range of 7 to 15 weeks). Nationally, mortality attributed to pneumonia and influenza exceeded 10.0% for four consecutive weeks, peaking at 10.8% during the week ending January 20, 2018.

CDC estimates that the burden of illness during the 2017–2018 season was high with an estimated 45 million people getting sick with influenza, 21 million people going to a health care provider, 810,000 hospitalizations, and 61,000 deaths from influenza (Table 1). The number of cases of influenza-associated illness that occurred during 2017-2018 was the highest since the 2009 H1N1 pandemic, when an estimated 60 million people were sick with influenza (7).