This is what wikipedia says. It doesn’t sound particularly uncommon.
“During seasonal epidemics, it is estimated that about 80% of otherwise healthy people who have a cough or sore throat have the flu.”
“During seasonal epidemics, it is estimated that about 80% of otherwise healthy people who have a cough or sore throat have the flu.”
> During seasonal influenza epidemics, diagnosis on the basis of clinical presentation has reasonable accuracy in previously healthy young and middle-aged adults, in whom the presence of fever with either cough or sore throat is associated with influenza virus infection in ~80% of patients.
So Wikipedia doesn’t add that this statement is about the accuracy of diagnosis by a clinician, and completely ignores the important symptom of a fever.
Just prior to the statement referring to 80%, Wikipedia also states the following, with references:
> In a typical year, influenza viruses infect 5–15% of the global population