Why did the flu kill 80,000 Americans last year?
The 2017-2018 flu season was historically severe. Public health officials estimate that 900,000 Americans were hospitalized and 80,000 died from the flu and its complications. For comparison, the previous worst season from the past decade, 2010-2011, saw 56,000 deaths. In a typical season, 30,000 Americans die.
So why was the 2017-2018 season such a bad year for flu? There were two big factors.
First, one of the circulating strains of the influenza virus, A(H3N2), is particularly virulent, and vaccines targeting it are less effective than those aimed at other strains. In addition, most of the vaccine produced was mismatched to the circulating A(H3N2) subtype.
Flu virus is a quick change artist.
Influenza is not a single, static virus. There are three species A, B and C that can infect people. A is the most serious and C is rare, producing only mild symptoms.
https://www.rawstory.com/2018/10/flu-kill-80000-americans-last-year/