[blueline]

how do you think they measure (roughly) how many people got the flu in previous years?

[pwg]

By estimation:

From the article:

"the Centers for Disease Control and Prevention estimated there were roughly 22,000 deaths in the prior season and 34,000 two seasons ago." -- emphasis added

[ineedasername]

Yes, and that same estimation methodology shows is has decreased significantly. But if you want firm numbers, here's your source: https://www.cdc.gov/flu/weekly/weeklyarchives2019-2020/Week0...

[davidcuddeback]

Estimation usually involves gathering data and applying some statistics to the data. The question was about the details of that process. "They estimated" isn't telling us anything new.