Also known as pyrexia or controlled hyperthermia is a common medical sign characterized by an elevation of temperature above the normal range of 36.5–37.5 °C (98–100 °F) due to an increase in the body temperature regulatory set-point. A fever is one of the body's immune responses that attempts to neutralize a bacterial, viral or other microbiological agents. As a temperature increases, there is general feeling of cold despite an increasing body temperature. With the exception of very high temperatures, treatment to reduce fever is often not necessary. Types The pattern of temperature changes may occasionally hint at the diagnosis: • Intermittent fever: Elevated temperature is present only for some hours of the day and becomes normal for remaining hours, e.g., malaria, kala-azar, pyaemia, or septicemia. • Pel-Ebstein fever: A specific kind of fever associated with Hodgkin's lymphoma, • Continuous fever: Temperature remains above normal throughout the day and does not fluctuate more than 1 °C in 24 hours, e.g. lobar pneumonia, typhoid, urinary tract infection, brucellosis, or typhus. • Remittant fever: Temperature remains above normal throughout the day and fluctuates more than 1 °C in 24 hours, e.g., infective endocarditis. • A neutropenic fever, Because of the lack of infection-fighting neutrophils, a bacterial infection can spread rapidly; this fever is, therefore, usually considered a medical emergency. Commonly seen in people receiving immune-suppressing chemotherapy than in apparently healthy people. • Febricula is a mild fever of short duration, of indefinite origin, and without any distinctive pathology. Hyperpyrexia Hyperpyrexia is a fever with an extreme elevation of body temperature greater than or equal to 41.5 °C (106.7 °F). Such a high temperature is considered a medical emergency as it may indicate a serious underlying condition or lead to significant side effects. Causes: 1. intracranial hemorrhage 2. sepsis 3. Kawasaki syndrome 4. neuroleptic malignant syndrome 5. drug effects 6. serotonin syndrome 7. Thyroid storm. Infections commonly associated with hyperpyrexia include: 1. roseola 2. rubeola 3. enteroviral infections
The following are some of the symptoms of Fever: A fever is usually accompanied by sickness behavior, which consists of lethargy, depression, anorexia, sleepiness, hyperalgesia, and the inability to concentrate. Differential diagnosis Fever is a common symptom of many medical conditions: • Infectious disease, e.g., influenza, HIV, malaria, infectious mononucleosis, or gastroenteritis • Various skin inflammations, e.g., boils, or abscess • Immunological diseases, e.g., lupus erythematosus, sarcoidosis, inflammatory bowel diseases, Kawasaki disease • Tissue destruction, which can occur in hemolysis, surgery, infarction, crush syndrome, rhabdomyolysis, cerebral hemorrhage, etc. • Reaction to incompatible blood products • Cancers, most commonly kidney cancer and leukemia and lymphomas • Metabolic disorders, e.g., gout or porphyria • Thrombo-embolic processes, e.g., pulmonary embolism or deep venous thrombosis Persistent fever that cannot be explained after repeated routine clinical inquiries is called fever of unknown origin. Temperature is ultimately regulated in the hypothalamus. A trigger of the fever, called a pyrogen, causes a release of prostaglandin E2 (PGE2). PGE2 then in turn acts on the hypothalamus, which generates a systemic response back to the rest of the body, causing heat-creating effects to match a new temperature level. Pyrogens A pyrogen is a substance that induces fever. 1. internal (endogenous) 2. Cytokines produced by phagocytic cells, are a part of the innate immune system. 3. interleukin 1 (α and β) 4. interleukin 6 (IL-6) 5. Tumor necrosis factor-alpha. 6. interleukin-8, 7. tumor necrosis factor-β 8. macrophage inflammatory protein-α 9. Macrophage inflammatory protein-β 10. interferon-α 11. interferon-β 12. Interferon-γ. 13 external (exogenous). • The bacterial substance lipopolysaccharide (LPS), present in the cell wall of some bacteria, is an example of an exogenous pyrogen. Pyrogenicity can vary. superantigens Body response after hypothalamic effect: • Increased heat production by increased muscle tone, shivering, and hormones like epinephrine • Prevention of heat loss, such as vasoconstriction. fever has several important functions in the healing process: • Increased mobility of leukocytes • Enhanced leukocytes phagocytosis • Endotoxin effects decreased • Increased proliferation of T cells
Fever should not necessarily be treated. Most people recover without specific medical attention. In general, people are advised to keep adequately hydrated. Oral rehydration solutions or water are generally used for this purpose. Excessive water may lead however to hyponatremia. If the temperature reaches the level of hyperpyrexia aggressive cooling is required. Medications The antipyretic : acetaminophen / paracetamol in children however both may be used together.