fever (redirected from of unknown origin fever)

Fever 

Definition

A fever is any body temperature elevation over 100 °F (37.8 °C).

Description

A healthy person's body temperature fluctuates between 97 °F (36.1 °C) and 100 °F (37.8 °C), with the average being 98.6 °F (37 °C). The body maintains stability within this range by balancing the heat produced by the metabolism with the heat lost to the environment. The "thermostat" that controls this process is located in the hypothalamus, a small structure located deep within the brain. The nervous system constantly relays information about the body's temperature to the thermostat, which in turn activates different physical responses designed to cool or warm the body, depending on the circumstances. These responses include: decreasing or increasing the flow of blood from the body's core, where it is warmed, to the surface, where it is cooled; slowing down or speeding up the rate at which the body turns food into energy (metabolic rate); inducing shivering, which generates heat through muscle contraction; and inducing sweating, which cools the body through evaporation.

A fever occurs when the thermostat resets at a higher temperature, primarily in response to an infection. To reach the higher temperature, the body moves blood to the warmer interior, increases the metabolic rate, and induces shivering. The "chills" that often accompany a fever are caused by the movement of blood to the body's core, leaving the surface and extremities cold. Once the higher temperature is achieved, the shivering and chills stop. When the infection has been overcome or drugs such as aspirin or acetaminophen (Tylenol) have been taken, the thermostat resets to normal and the body's cooling mechanisms switch on: the blood moves to the surface and sweating occurs.

Fever is an important component of the immune response, though its role is not completely understood. Physicians believe that an elevated body temperature has several effects. The immune system chemicals that react with the fever-inducing agent and trigger the resetting of the thermostat also increase the production of cells that fight off the invading bacteria or viruses. Higher temperatures also inhibit the growth of some bacteria, while at the same time speeding up the chemical reactions that help the body's cells repair themselves. In addition, the increased heart rate that may accompany the changes in blood circulation also speeds the arrival of white blood cells to the sites of infection.

Causes and symptoms

Fevers are primarily caused by viral or bacterial infections, such as pneumonia or influenza. However, other conditions can induce a fever, including allergic reactions; autoimmune diseases; trauma, such as breaking a bone; cancer; excessive exposure to the sun; intense exercise; hormonal imbalances; certain drugs; and damage to the hypothalamus. When an infection occurs, fever-inducing agents called pyrogens are released, either by the body's immune system or by the invading cells themselves, that trigger the resetting of the thermostat. In other circumstances, the immune system may overreact (allergic reactions) or become damaged (autoimmune diseases), causing the uncontrolled release of pyrogens. A stroke or tumor can damage the hypothalamus, causing the body's thermostat to malfunction. Excessive exposure to the sun or intensely exercising in hot weather can result in heat stroke, a condition in which the body's cooling mechanisms fail. Malignant hyperthermia is a rare, inherited condition in which a person develops a very high fever when given certain anesthetics or muscle relaxants in preparation for surgery.

How long a fever lasts and how high it may go depends on several factors, including its cause, the age of the patient, and his or her overall health. Most fevers caused by infections are acute, appearing suddenly and then dissipating as the immune system defeats the infectious agent. An infectious fever may also rise and fall throughout the day, reaching its peek in the late afternoon or early evening. A low-grade fever that lasts for several weeks is associated with autoimmune diseases such as lupus or with some cancers, particularly leukemia and lymphoma.

A dramatic rise in body temperature often includes the following symptoms: A. Loss of fluid results in dehydration. B. The hypothalamic set-point is increased, raising metabolism. C. Blood vessels in skin dilate. D. Sweat glands produce excess perspiration. E. Increased pulse rate. F. Increased hypothalmic set-point may introduce chills and shivering to promote heat production from muscles. G. Skin becomes more heat-sensitive.

(Illustration by Electronic Illustrators Group.)

Diagnosis

A fever is usually diagnosed using a thermometer. A variety of different thermometers are available, including traditional glass and mercury ones used for oral or rectal temperature readings and more sophisticated electronic ones that can be inserted in the ear to quickly register the body's temperature. For adults and older children, temperature readings are usually taken orally. Younger children who cannot or will not hold a thermometer in their mouths can have their temperature taken by placing an oral thermometer under their armpit. Infants generally have their temperature taken rectally using a rectal thermometer.

As important as registering a patient's temperature is determining the underlying cause of the fever. The presence or absence of accompanying symptoms, a patient's medical history, and information about what he or she may have ingested, any recent trips taken, or possible exposures to illness help the physician make a diagnosis. Blood tests can aid in identifying an infectious agent by detecting the presence of antibodies against it or providing samples for growth of the organism in a culture. Blood tests can also provide the doctor with white blood cell counts. Ultrasound tests, magnetic resonance imaging (MRI) tests, or computed tomography (CT) scans may be ordered if the doctor cannot readily determine the cause of a fever.

Treatment

Physicians agree that the most effective treatment for a fever is to address its underlying cause, such as through the administration of antibiotics. Also, because a fever helps the immune system fight infection, it usually should be allowed to run its course. Drugs to lower fever (antipyretics) can be given if a patient (particularly a child) is uncomfortable. These include aspirin, acetaminophen (Tylenol), and ibuprofin (Advil). Aspirin, however, should not be given to a child or adolescent with a fever since this drug has been linked to an increased risk of Reye's syndrome. Bathing a patient in cool water can also help alleviate a high fever.

A fever requires emergency treatment under the following circumstances:

• newborn (three months or younger) with a fever over 100.5 °F (38 °C)
• infant or child with a fever over 103 °F (39.4 °C)
• fever accompanied by severe headache, neck stiffness, mental confusion, or severe swelling of the throat

A very high fever in a small child can trigger seizures (febrile seizures) and therefore should be treated immediately. A fever accompanied by the above symptoms can indicate the presence of a serious infection, such as meningitis, and should be brought to the immediate attention of a physician.

Prognosis

Most fevers caused by infection end as soon as the immune system rids the body of the pathogen and do not produce any lasting effects. The prognosis for fevers associated with more chronic conditions, such as autoimmune disease, depends upon the overall outcome of the disorder.

Resources

Books

Gelfand, Jeffrey. "Fever, Including Fever of Unknown Origin." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

Key terms

Antipyretic — A drug that lowers fever, like aspirin or acetaminophen.

Autoimmune disease — Condition in which a person's immune system attacks the body's own cells, causing tissue destruction.

Febrile seizure — Convulsions brought on by fever.

Malignant hyperthermia — A rare, inherited condition in which a person develops a very high fever when given certain anesthetics or muscle relaxants in preparation for surgery.

Meningitis — A potentially fatal inflammation of the thin membrane covering the brain and spinal cord.

Metabolism — The chemical process by which the body turns food into energy, which can be given off as heat.

Pyrogen — A chemical circulating in the blood that causes a rise in body temperature.

Reye's syndrome — A disorder principally affecting the liver and brain, marked by the rapid development of life-threatening neurological symptoms.

---

fever /fe·ver/ (fe´ver)

1. pyrexia; elevation of body temperature above the normal (37°C).

2. any disease characterized by elevation of body temperature.

---

blackwater fever  a dangerous complication of falciparum malaria, with passage of dark red to black urine, severe toxicity, and high mortality.

boutonneuse fever  a tickborne disease endemic in the Mediterranean area, Crimea, Africa, and India, due to infection with Rickettsia conorii, with chills, fever, primary skin lesion (tache noire), and rash appearing on the second to fourth day.

cat-scratch fever  see under disease.

central fever  sustained fever resulting from damage to the thermoregulatory centers of the hypothalamus.

childbed fever  puerperal septicemia.

Colorado tick fever  a tickborne, nonexanthematous, febrile, viral disease caused by an arenavirus and seen in the Rocky Mountain area of the United States.

continued fever  one that varies only slightly in 24 hours.

Crimean-Congo hemorrhagic fever  a hemorrhagic fever caused by the Crimean-Congo hemorrhagic fever virus, transmitted by ticks and by contact with blood, secretions, or fluids from infected animals or humans; it occurs in the Crimea, Central Asia, and regions of Africa.

drug fever  febrile reaction to a therapeutic agent, such as a vaccine, antineoplastic, or antibiotic.

elephantoid fever  a recurrent acute febrile condition occurring with filariasis; it may be associated with elephantiasis or lymphangitis.

enteric fever  any of a group of febrile illnesses associated with enteric symptoms caused by salmonellae, especially typhoid fever and paratyphoid fever.

epidemic hemorrhagic fever  an acute infectious disease characterized by fever, purpura, peripheral vascular collapse, and acute renal failure, caused by viruses of the genus Hantavirus, thought to be transmitted to humans by contact with saliva and excreta of infected rodents.

familial Mediterranean fever  a hereditary disease usually seen in Armenians and Sephardic Jews, with short recurrent attacks of fever, pain in the abdomen, chest, or joints, and erythema like that of erysipelas; it may be complicated by amyloidosis.

Haverhill fever  the bacillary form of rat-bite fever, due to Streptobacillus moniliformis, and transmitted through contaminated raw milk and its products.

hay fever  a seasonal form of allergic rhinitis, with acute conjunctivitis, lacrimation, itching, swelling of the nasal mucosa, nasal catarrh, and attacks of sneezing, an anaphylactic or allergic reaction excited by a specific allergen (such as pollen).

hemorrhagic fevers  a group of diverse, severe viral infections seen around the world but mainly in the tropics, usually transmitted to humans by arthropod bites or contact with virus-infected rodents; they all have certain common features, including fever, hemorrhagic manifestations, thrombocytopenia, shock, and neurologic disturbances.

humidifier fever  malaise, fever, cough, and myalgia caused by inhalation of air that has been passed through humidifiers, dehumidifiers, or air conditioners contaminated by fungi, amebas, or thermophilic actinomycetes.

intermittent fever  an attack of malaria or other fever, with recurring fever episodes separated by times of normal temperature.

Katayama fever  fever associated with severe schistosomal infections, accompanied by hepatosplenomegaly and by eosinophilia.

Lassa fever  a highly fatal, acute, febrile disease seen in West Africa, caused by a virulent arenavirus and characterized by increasing prostration, sore throat, ulcerations of the mouth or throat, rash, and general aching.

metal fume fever  a disease of welders and others working with volatilized metals, marked by sudden thirst, metallic taste in the mouth, high fever with chills, sweating, and leukocytosis.

mud fever  a type of leptospirosis seen in workers in flooded fields and swamps in Germany and Russia.

nonseasonal hay fever , hay fever, perennial nonseasonal allergic rhinitis.

Oroya fever  see Carrión's disease.

paratyphoid fever  paratyphoid.

parenteric fever  a disease clinically resembling typhoid fever and paratyphoid, but not caused by Salmonella.

parrot fever  psittacosis.

pharyngoconjunctival fever  an epidemic disease due to an adenovirus, seen mainly in school children, with fever, pharyngitis, conjunctivitis, rhinitis, and enlarged cervical lymph nodes.

phlebotomus fever  a febrile viral disease of short duration, transmitted by the sandfly Phlebotomus papatasi, with dengue-like symptoms, seen in Mediterranean and Middle Eastern countries.

Pontiac fever  a self-limited disease marked by fever, cough, muscle aches, chills, headache, chest pain, confusion, and pleuritis, caused by a strain of Legionella pneumophila.

pretibial fever  an infection due to a serovar of Leptospira interrogans, marked by a rash on the pretibial region, with lumbar and postorbital pain, malaise, coryza, and fever.

puerperal fever  septicemia accompanied by fever, in which the focus of infection is a lesion of the mucous membrane of the parturient canal due to trauma during childbirth; usually due to a streptococcus.

Q fever  a febrile rickettsial infection, usually respiratory, first described in Australia, caused by Coxiella burnetii.

rat-bite fever  either of two clinically similar acute infectious diseases, usually transmitted through a rat bite, one form (bacillary) of which is caused by Streptobacillus moniliformis and the other form (spirillary) by Spirillum minor.

recurrent fever 

1. relapsing f.

2. recurrent paroxysmal fever occurring in various diseases, such as malaria.

relapsing fever  any of a group of infectious diseases due to various species of Borrelia, marked by alternating periods of fever and apyrexia, each lasting from five to seven days.

remittent fever  one that shows significant variations in 24 hours but without return to normal temperature.

rheumatic fever  a febrile disease occurring as a sequela to Group A hemolytic streptococcal infections, characterized by multiple focal inflammatory lesions of connective tissue structures, especially of the heart, blood vessels, and joints, and by Aschoff bodies in the myocardium and skin.

Rift Valley fever  a zoonotic febrile disease with dengue-like symptoms, due to an arbovirus, transmitted to humans by mosquitoes or by contact with diseased animals; first observed in the Rift Valley, Kenya.

Rocky Mountain spotted fever  infection with Rickettsia rickettsii, transmitted by ticks, marked by fever, muscle pain, and weakness followed by a macular petechial eruption that begins on the hands and feet and spreads to the trunk and face, with other symptoms in the central nervous system and elsewhere.

rose fever  a form of hay fever caused by grass pollens released while roses or other flowers are blooming.

scarlet fever  an acute disease caused by Group A β-hemolytic streptococci, marked by pharyngotonsillitis and a skin rash caused by an erythrogenic toxin produced by the organism; the rash is a diffuse, bright red erythema, and desquamation of the skin begins as fine scaling with eventual peeling of the palms and soles.

Sennetsu fever  a febrile disease seen in Japan and Malaysia and caused by Ehrlichia sennetsu, characterized by headache, nausea, lymphocytosis, and lymphadenopathy.

septic fever  fever due to septicemia.

South African tickbite fever  boutonneuse f.

trench fever  a louse-borne rickettsial disease due to Bartonella quintana, transmitted by the body louse, Pediculus humanus corporis, and characterized by intermittent fever, generalized aches and pains, particularly severe in the shins, chills, sweating, vertigo, malaise, typhus-like rash, and multiple relapses.

typhoid fever  infection by Salmonella typhi chiefly involving the lymphoid follicles of the ileum, with chills, fever, headache, cough, prostration, abdominal distention, splenomegaly, and a maculopapular rash; perforation of the bowel may occur in untreated cases.

fever of unknown origin  (FUO) a febrile illness of at least three weeks' duration (some authorities permit a shorter duration), with a temperature of at least 38.3°C on at least three occasions and failure to establish a diagnosis in spite of intensive inpatient or outpatient evaluation (three outpatient visits or three days' hospitalization).

West Nile fever  see under encephalitis.

yellow fever  an acute, infectious, mosquito-borne viral disease, endemic primarily in tropical South America and Africa, marked by fever, jaundice due to necrosis of the liver, and albuminuria.

---

fe·ver (fvr)

n.

1. Body temperature above the normal of 98.6°F (37°C). Also called pyrexia.

2. Any of various diseases in which there is an elevation of the body temperature above normal.

---

fever

Etymology: L, febris

an elevation of body temperature above the normal circadian range as a result of an increase in the body's core temperature. Fever is a temperature above 37.2° C (98.9° F) in the morning or above 37.7° C (99.9° F) in the evening. Fever results from an imbalance between the elimination and the production of heat. Exercise, anxiety, and dehydration may increase the temperature of healthy people. Infection, neurologic disease, malignancy, pernicious anemia, thromboembolic disease, paroxysmal tachycardia, congestive heart failure, crushing injury, severe trauma, and many drugs may cause fever. No single theory explains the mechanism whereby the temperature is increased. Fever has no recognized function in conditions other than infection. It increases metabolic activity by 7% per degree Celsius, requiring a greater intake of food. Convulsions may occur in children whose fevers tend to rise abruptly, and delirium is seen with high fevers in adults and in children. Very high temperatures, as in heatstroke, may be fatal. The course of a fever varies with the cause, the condition of the patient, and the treatment given. The onset may be abrupt or gradual, and the period of maximum elevation, called the stadium or fastigium, may last for a few days or up to 3 weeks. The fever may resolve suddenly, by crisis, or gradually, by lysis. Certain diseases and conditions are associated with fevers that begin, rise, and fall in such characteristic curves that diagnosis may be made by studying a graphic record of the course of the fever. Kinds of hyperthermia include habitual fever, intermittent fever, and relapsing fever. Also called febrile response. See also fever treatment, hyperpyrexia, quartan malaria, remittent fever, septic fever, tertian malaria.

---

fever,

n condition characterized by a rise in body temperature. Most fevers are mild and can be treated at home, but if they last more than two days, if the temperature rises to over 102.2° F, or if body temperature suddenly rises to 102.2° F within four hours, it is considered dangerous, and professional treatment should be sought immediately.

---

fever (pyrexia)

(pīrek´sē),
n an elevation of the body temperature.

hand-foot-and-mouth fever, aphthous,

n See disease.

fever, cat-scratch,

n See disease, cat-scratch.

fever, hay,

n rhinitis and conjunctivitis resulting from allergy; frequently caused by allergy to pollens.

fever, of unknown origin,

n the persistent elevation of body temperature without an identifiable cause.

fever, rheumatic

n a severe, apparently infectious disease produced by hemolytic streptococci organisms or associated with their presence in the body; characterized by upper respiratory tract inflammation, cervical lymphadenopathy and lymphadenitis, polyarthritis, cardiac involvement, and subcutaneous nodules. The disease may be produced by an autoantibody reaction.

fever, scarlet (scarlatina),

n an acute disease caused by a specific type of
Streptococcus organism and characterized by a rash and strawberry tongue.

fever, uveoparotid (Heerfordt's syndrome, uveoparotitis)

n 1. a disease characterized by inflammation of the parotid gland and of the uveal regions of the eye.
2. the firm, nodular enlargement of the parotid glands, uveitis, and cutaneous lesions may be present. Considered to be a form of sarcoidosis.
3. a syndrome consisting of sarcoidosis affecting the parotid glands, inflammation of the lacrimal glands, and inflammation of the uveal tract of the eye.

---

fever

1. an abnormally high body temperature; pyrexia. See also hyperthermia.

2. any disease characterized by marked increase of body temperature. See body temperature.

For diseases characterized by fever, see the eponymic or descriptive name: e.g. african swine, bovine petechial, canicola, cat-scratch disease, desert, ephemeral, equine intestinal ehrlichiosis, classical swine fever(hog cholera), malignant catarrhal fever, malta, mediterranean coast, q, rift valley, rocky mountain spotted, Russian spring-summer encephalitis, tickborne, tularemia, undulant. milk fever is not accompanied by pyrexia.

---

aseptic fever

fever associated with aseptic wounds, presumably due to the disintegration of leukocytes or to the absorption of avascular or traumatized tissue.

central fever

sustained fever resulting from damage to the thermoregulatory centers of the hypothalamus.

chemical fever

fever caused by the intake of a sterile substance, e.g. the injection of a foreign protein, the administration of dinitrophenols.

continued fever, continuous fever

persistently elevated body temperature, showing no or little variation and never falling to normal during any 24-hour period.

intermittent fever

an attack of fever, with recurring paroxysms of elevated temperature separated by intervals during which the temperature is normal.

remittent fever

elevated body temperature showing fluctuation each day, but never falling to normal.

septic fever

see septic fever.

Shar Pei fever

see familial renal amyloidosis.

fever of unknown origin (FUO)

a recognized clinical syndrome of persistently (>2 weeks) elevated body temperature (>104°F) and without other signs. Causes include infections, neoplasia, immune-mediated diseases, and drug reactions.

---

fever

Internal medicine A body temperature of ≥ 37.2ºC/99.0ºF in early morning or ≥ 37.8ºC/100.0ºF in the evening that is a complex and coordinated adaptive response, which is part of the reaction to an immune challenge; this response is stereotyped, and largely independent of a causitive agent; as with other integrated responses–eg, regulation of energy metabolism, BP and volume, and reproduction, fever depends on humoral cues and is orchestrated by the hypothalamus, which coordinates autonomic, behavioral, endocrine, and metabolic responses– when corporal temperature is raised by endogenous pyrogen, T cell production ↑ 20-fold; endogenous pyrogen also shifts iron–needed by bacteria away from plasma; hyperthermia–up to 40ºC may trigger CA regression. See 'Animal House fever' Argentine hemorrhagic fever, Blackwater fever, Blue fever, Breakbone fever, Bolivian hemorrhagic fever, Bullis fever, Cabin fever, Cat-bite fever, Coley's toxin, Colorado tick fever, Congo-Crimean hemorrhagic fever, Cotton fever, Dehydration fever, Dengue hemorrhagic fever, Epidemic louse-borne typhus fever, Familial hibernian fever, Familial Mediterranean fever, Filarial fever, Fort Bragg fever, Haverhill fever, Hay fever, Hectic-septic fever, Hypothalamic fever, Izumi fever, Korean hemorrhagic fever, Lassa fever, Malta fever, Mediterranean fever, Metal fume fever, Omsk hemorrhagic fever, O'nyong-nyong fever, Polymer fume fever, Pontiac fever, Potamic fever, Q fever, Quartan fever, Quintan fever, Rat-bite fever, Relapsing fever, Rheumatic fever, Rift Valley fever, Rocky Mountain spotted fever, Sandfly fever, Scarlet fever, Seven-day fever, Simian hemorrhagic fever, Spring fever, Swamp fever, Tertian fever, Thirteen day fever, Three day fever, Trench fever, Valley fever, West Nile fever, Yellow fever.

---

Patient discussion about of unknown origin fever.

Q. High Fever - is it dangerous? high fever over a long period can be dangerous. on the other hand it shows also that your body is working like Superman...

A. the heart surgeon knows, that if he touchs during a heart-operation this sparkle of 96°C, the patient will die. exitus for sure! the problem for the heart surgeon is, that he don't know why it is so. this is the big problem you can have with a doctor who don't know about such things. if you like to know more about this sparkle and why the patient dies, write me a mail and i will share with you a link to read about it. ask me if you don't understand me for what i try to teach you. FEVER is a healing-system nature gave us. Let it work naturally. don't make a tonsillectomy just because some do or because it is a fashion. think first about it. your tonsils have functions and we need them. they are not just decoration. my parents forced me to make a tonsillectomy because they were told to do so because i had many otitis. i would never do it to my kids. i have since 30 years from time to time pain there and i loose some blood. it hurts terribly when it is acute.

Q. Why is it hard to swallow when you have a sore throat? I was sick last week. I had a sore throat pain in my neck and fever. the most annoying symptom that i had was pain during sallowing. what is the source of that pain, and what can I do to ease it next time?

A. When you have an inflammation in your body, the sick area hurts when its palpated. when your neck is inflamed, you have a pain in the neck. when the inside part of the neck is inflamed you have tonsillitis.
When you eat something, it touches your inside of the neck, and if it's inflamed it will be painful.
The good news is that you can treat this pain in the same way you treat other inflammatory pain - hot (NOT boiling) tea.

Q. Does Isoniazid cause Lupus? I work in a Hospital and have been in contact with a patient who suffers from TB (tuberculosis). I was put under surveillance and now have to take Isoniazid in order to prevent developing TB. I read that this medicine can cause Lupus. Is this true?

A. Isoniazid can cause drug-induced lupus (DIL). However, there is a difference between DIL and systemic lupus. Systemic lupus is irreversible, whereas drug-induced lupus generally is reversible when the drug is discontinued. The symptoms of drug-induced lupus generally do not include kidney involvement or central nervous system involvement.