I looked up some stats. Roughly 6,000 people die each day in the US. Depending on the time of the year, one in ten of those is due to the flu or flu related illness like pneumonia. (Probably the majority of these are elderly people who would have died shortly of something else had the flu not gotten them first.)
Here’s an interesting article.
https://www.bloomberg.com/news/articles/2018-02-09/flu-caused-1-in-10-american-deaths-last-week
I guess that explains why millions of people (including American servicemen) died of the Spanish flu during WWI.
Actually about 7,000 Americans die each winter month. About 6,400 die each summer month. The difference? Flu and other respiratory ailments, heart failure as cold weather constricts blood flow, etc. Even cancer deaths are a bit higher in winter.