Fever can be triggered by several factors, including infections, nervous system disorders, certain cancers, blood diseases like leukemia, embolism, thrombosis, heatstroke, dehydration, surgical trauma, crushing injuries, and allergic reactions.

Here are the different types of fever:

• Rigor: This type of fever is characterized by a sudden and severe attack of shivering, during which body temperature quickly rises to hyperpyrexia levels.
• Hyperthermia: Occurs when the body temperature exceeds 104°F (40°C) due to intense heat exposure or excessive heat generation, overwhelming the body's thermoregulatory mechanisms.
• Malignant Hyperthermia: A genetic disorder associated with uncontrolled heat production that occurs when susceptible individuals are exposed to certain anesthetic medications.
• Heatstroke: Identified by a body temperature of 104°F (40°C) or higher, hot, dry skin, and central nervous system abnormalities, such as confusion, seizures, or loss of consciousness.
• Neurogenic Fever results from damage to the hypothalamus caused by conditions like cerebral trauma, intracranial hemorrhage, or elevated intracranial pressure. This type of fever does not respond to antipyretic (fever-reducing) drugs.
• Fever of Unknown Origin (FUO): This is defined as a fever of 101°F (38.3°C) or higher that persists for three weeks or longer without an identifiable cause after initial investigation.