I am responding to two claims: 1) that influenza knocks you out and anything that doesn’t isn’t influenza; 2) that flu even means influenza in common usage, and so appeals to influenza symptoms are meaningless.
> typically characterised by
What are you basing this on? I have only found estimates of asymptomatic infection, but do you have any studies that performed a random sample of the population looking at disease severity by positive PCR?
Covid was a much more severe illness with very little endemic immunity and we still saw dramatic variation in outcome. It seems to be estimated that a third of influenza infections are asymptomatic - do you propose that the distribution is entirely bimodal and that everyone else had severe symptoms? This seems implausible given the broad (and highly differentiated by prior variant) level of population immunity.
The only studies I could find (with an admittedly cursory search) look at people already suffering from ILI and testing the likelihood that the ILI is influenza, which does not tell you what proportion of people experience mild symptoms with influenza infection. It does however tell you that many of these people are not suffering from influenza, but would have likely said they had “flu” and met your criteria.
My point therefore is that “flu” doesn’t mean influenza, since there’s no common definition that is either sufficient or necessary to correctly identify an influenza infection, and we do not require a PCR test to use the term. It therefore means a severe non-specific viral illness, or perhaps an “influenza like illness”
It also means criticising people for using the term for a mild illness is probably fair, but not because it doesn’t meet the criteria of being influenza, and I really wish people would stop using this kind of argumentation about it, as though they have any idea what a specific influenza infection looks like.