What could cause fever with normal C-reactive protein levels?

C-reactive protein (CRP), also known as an acute-phase protein, is a substance in plasma that rises rapidly in response to bodily injury or infection. It plays a role in activating the complement system and enhancing phagocytosis by acting as an opsonin. CRP is also a non-specific marker of inflammation. When CRP levels are normal but fever is present, the patient may have a viral respiratory infection. In cases of mycoplasma or bacterial infections, CRP levels typically increase. If CRP remains normal despite fever, the cause is generally considered to be a viral infection, and treatment should follow medical guidance, including antiviral therapy and symptomatic management.