Delirium and fever. Those symptoms mean a consequence of temperature raising far above the normal level. Human body temperature fluctuates during a day starting from 98.6 degrees Fahrenheit and few degrees above. The lowest body temperature usually is observed just before down and the highest raises up about an afternoon. Delirium is often a sign of actively working the immune system. Fever and delirium is a precursor of the immune system’s fight against the incoming infection, viruses, and bacteria, which are temperature unstable.