I had to look up morbidity - the condition of being diseased (I’m not sure I knew that).
The following is what I got off the CDC website. Except reading it again, I’m guessing they are saying out of all deaths during the 16 week flu season, deaths by flu were 10% of the deaths. I was thinking it was 10% rate of those who got the flu. (No wonder I thought it seemed high).
“During the 2017-2018 season, the percentage of deaths attributed to pneumonia and influenza (P&I) 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 P&I exceeded 10.0% for four consecutive weeks, peaking at 10.8% during the week ending January 20, 2018.”
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Hmm. The following article said there were 90,000 deaths in the USA last year due to flu, with 900,000 being hospitalized - so that is 10%. Although how many millions got the flu and didn’t go to the hospital?
https://www.cnn.com/2018/09/26/health/flu-deaths-2017—2018-cdc-bn/index.html
In the course of a bad but not severe influenza season, about one in ten are infected (morbidity), and, of those, one in one thousand or fewer die - mortality (sometimes a lot fewer, which gives the discrepancy in reported rates). And the overall population mortality is a magnitude give or take lower.