Earlier quoted context omitted.
Flu characteristics are well understood and you should encounter no obstacles in doing that research yourself.
Okay: > Uncomplicated influenza signs and symptoms typically resolve after 3-7 days for the majority of people, although cough and malaise can persist for >2 weeks, especially in elderly people and those with chronic lung disease. https://www.cdc.gov/flu/professionals/acip/clinical.htm Seems like over 14 days of flu symptoms is common.
Precisely what overall percentage of flu patients across the general population experience continuing symptoms after 14-21 days?
(Any common influenza in any typical year in the past decade is fine.)