I wouldn't call post #2237089 or post #618431 sick, though it's still related to fever. It's an anime trope where a clueless person checks someone else (usually a romantic interest) for a fever because he or she is blushing.
If this implication were to pass, fever needs to be narrowly defined (in bed, cold pad, thermometer, etc.) and a tag needs to happen for the above-mentioned visual.