Fever slightly increases immune reactions, increases chemotactic, phagocytic, and bactericidal activity of polymorphonuclear leucocytes. Up to certain value, it stimulates the processes of antibody production. Concomitantly, it slows down the proliferation of microorganisms. Increased body temperature causes a decrease in the amount of plasmatic iron, zink, and copper. This decrease is not favourable for the growth of microbes.
High temperature causes destruction of lysosomes and the whole cells.
This is a way by which the body defendes itself against microbes but also against reglication of viruses. The increased production of interferons also acts against viruses. In general, fever is considered to be a pathological reaction. However, it belongs to compensatory mechanisms and has important roles in defence processes. Therefore, medication of actual fever can't be the target of treatment.