Fever

About

A body temperature of more than 37.2�C or 98.9�F in the morning or a temperature of more than 37.7� or 99.9�F in the evening indicates fever.

Fever is a symptom that has plagued each of us at some time or the other. Often, people try to treat fever at home. A better understanding about fever will no doubt help in managing fever better at home; it will also ensure that a doctor is consulted at the right time.

Man is a warm-blooded animal, that is, body temperature is maintained regardless of the environmental temperature. The normal temperature of the body is maintained at 37�C or 98.6�F by the hypothalamus, a small but important part situated just below the brain. A slight variation of 0.5�C or 0.9�F occurs during the day.

Fever is defined as a before-noon temperature of more than 37.2�C or 98.9�F or an afternoon temperature of more than 37.7�C or 99.9�F. Fever is an elevation in normal body temperature that occurs in connection with a raised hypothalamic set point.

Body temperature is measured using a thermometer. The reading is obtained either by placing a thermometer in the mouth, in the rectum (especially in children), from the ear near the ear drum or in the armpit. Rectal temperatures are usually 0.5�C or 0.7�F higher than oral temperatures. Temperatures taken in the armpit are usually not very reliable.

Very high temperature of more than 41.5�C or 106.7�F is called hyperpyrexia. It occurs due to brain hemorrhage or severe infections.

Some causes of fever are listed below:

• Infections: Viral, bacterial, fungal or protozoal infections often cause fever. Some additional features that can help in the diagnosis of fever due to infections are:
• Fever of short duration without specific symptoms may be due to influenza
• Fever with throat pain and difficulty in swallowing could be due to sore throat infection, diphtheria or infectious mononucleosis (infection by a virus called Epstein-Barr virus)
• Fever with cough, chest pain and rusty sputum may be due to pneumonia
• Fever with rigors and burning while passing urine indicates a urinary tract infection
• An alternate day fever with rigors indicates malarial infection
• Fever with swelling of feet with rigors and a raised eosinophil count may indicate filariasis
• An increasing fever with pain in abdomen, small red spots on the skin and a slow heart rate could be due to typhoid
• Fever with neck stiffness, headache and vomiting may be due to meningeal infection (infection of the covering of the brain)
• Fever with cough over a long duration and weight loss may indicate tuberculosis

• Fever with rashes may be due to a viral infection
• Short-duration fever with progressive weight loss and a high-risk behavior could possibly be due to HIV infection
• Drugs and Biological Agents: Drugs like beta-lactam antibiotics, procainamide, isoniazid, alpha-methyldopa, quinidine and diphenylhydantoin are associated with fever. Biological agents like interferons and interleukins used in therapy could also cause fever. Vaccines could also result a temporary rise in temperature. Fever caused by drugs is often associated with a rash.
• Tissue injury: Heart attack, burns, trauma and injections into muscles damage tissues and can cause fever.
• Cancers: Blood cancers like leukemia and lymphoma, and liver cancer can cause fever. The liver, spleen and lymph nodes may be enlarged and easily felt in these conditions.

• Inflammatory diseases: Rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease are some inflammatory diseases that could cause a rise in body temperature.
• Hormonal diseases: Thyrotoxicosis (a condition in which the thyroid gland is hyperactive) and pheochromocytoma (a condition in which the adrenal gland is affected) can cause fever.
• Metabolic diseases: Gout and increase in blood urea can sometimes raise the body temperature.
• Genetic diseases: Familial Mediterranean fever is a genetic disease with fever as one of its symptoms.

References:

1. Harrison�s Principles of Internal Medicine
2. Nelson�s Textbook of Pediatrics
3. PJ Mehta�s Practical Medicine