NOTE: Not looking for real-life medical advice, though the question is inspired by me going through a weird two-week coughing spell last month.
Easiest example would be influenza. If you go to a doctor with several flu symptons, but absolutely no fever at all, will a diagnosis of “influenza” be dismissed out of hand? Would the absence of a fever mess up various kinds of infection diagnoses (i.e. “Nope, you can’t have Condition X because you have no fever … but wait! Your labs show wholesale infection! ”)?
Are there cases in the medical literature of folks being physiologically unable to muster up a fever in response to infection? If so, I assume that is a dangerous situation to be in, yes?
Last question: body temperature varies among healthy individuals as I understand it – 98.6 is “merely” an average, correct? If so, do the upper-end body-tempeature outliers get any kind of infection-fighting advantages from basically having a permanent low-grade fever? Do “never get sick” people typically walk around with body-temps of 99.2, none the wiser?