Nationally, the predominant virus — a particularly nasty strain, H3N2 — causes the worst outbreaks of the two types of influenza A viruses and two influenza B viruses that circulate among people.What many people don’t realize is that even after someone recovers from the flu, the inflammatory response generated by the virus continues to wreak havoc for another four to six weeks in those who are middle-aged and older, increasing the rate of heart attacks and strokes, Schaffner said.Influenza has not been a serious problem the last two years, experts and health officials have said, because of the masking, social distancing and other measures people took to protect themselves against covid-19.It’s hard to know how long the season will last, how severe it might be, and if different parts of the country will experience different levels of respiratory disease at different times.Chile got ahead of its bad flu season, which began months earlier than a typical season, by rapidly vaccinating 88 percent of its high-risk population before peak influenza activity, according to a CDC report this week."