II. Definitions

  1. Fever
    1. Standard criteria
      1. Temperature >38 C (100.4 F)
    2. Criteria in adults over age 65 years
      1. Fever: Temperature rise of 1.1 C (2 F) over baseline
      2. High fever suggesting severe infection: 38.3 C (101 F)
  2. Remittent Fever
    1. Daily elevated Temperature (>38 C or 100.4 F)
    2. Returns to baseline but not to normal
  3. Intermittent Fever (Periodic Fever, Relapsing Fever)
    1. Intermittently elevated Temperature (>38 C, 100.4 F)
    2. Return to baseline and to normal
    3. Examples
      1. PFAPA Syndrome: Fever every 3-4 weeks
        1. Most common cause in children age <5 years
      2. Relapsing Fever (Borrelia species): Every 2-3 weeks
      3. Malaria
        1. Plasmodium Vivax: fever at 48 hour intervals (Tertian Fever)
        2. Plasmodium Malariae: fever at 72 hour intervals (Quartan Fever)
      4. Rat Bite Fever: Fever every 3 to 5 days
      5. Hodgkin's Disease: Pel-Ebstein Fever
      6. Cyclic Neutropenia: Fever every 3 weeks
        1. Associated with Mucosal Ulcer
  4. Fever Peak Timing
    1. Fever typically peaks in the evening
    2. Morning fever peak
      1. Polyarteritis Nodosa
      2. Typhoid Fever
      3. Whipple Disease
    3. Twice daily fever peak
      1. Malaria
      2. Miliary Tuberculosis
      3. Still Disease
      4. Visceral Leishmaniasis
  5. Hectic Fever
    1. Daily elevated Temperature (>38 C or 100.4 F)
    2. Either remittent or intermittent pattern
    3. Temperature excursion >1.4 C (2.5 F)
    4. Examples
      1. Intermittent bacteremia (dental abscess, UTI)
      2. Epstein-Barr Virus
      3. Familial Mediterranean Fever
      4. Crohn's Disease
      5. Still's Disease (Juvenile Rheumatoid Arthritis)
  6. Sustained or Continuous Fever
    1. Daily elevated Temperature (>38 C or 100.4 F)
    2. Fluctuation of elevated Temperature < 0.3 C (0.5 F)
    3. Associated conditions
      1. Drug Fever
      2. Salmonella
  7. Pulse-Temperature Dissociation
    1. Pulse slower than normal for fever degree (pulse fails to increase with fever spike)
    2. Associated conditions
      1. Typhoid Fever
      2. Rickettsial infection
  8. Fever with Bradycardia (Facet Sign)
    1. See Pulse-Temperature Dissociation as above
    2. Associated conditions
      1. Central Nervous System Malignancy
      2. Lymphoma
      3. Typhoid Fever
      4. Yellow Fever

III. Pathophysiology

  1. Fever is an inflammatory response
    1. Endogenous pyrogens (inflammatory Cytokines) trigger the Hypothalamus to increase Body Temperature
    2. Fever is not synonymous with infection, as fever can be triggered by any systemic inflammatory response
  2. Fever is a host adaptive response to invading infection
    1. Increased Body Temperature increases immune function
    2. Increased Body Temperature decreases viral and Bacterial replication

IV. Classification

  1. Fever Without Focus
    1. Age <36 months
    2. Higher risk in younger infants
    3. Fever without localizing signs
    4. Acute onset of fever persisting <1 week
    5. Assess for Occult Bacteremia
  2. Fever of Unknown Origin (FUO)
    1. Fever exceeding 1 week duration
    2. Fever documented in the hospital
    3. All possible investigations performed during the week

V. Causes: Common Non-Infectious Causes of Low Grade Fever

  1. Over-dressing
  2. Recent Exercise
  3. Hot weather
  4. Warm foods
  5. Recent Immunization
    1. DTP Vaccine within 24 hours
    2. MMR Vaccine within 7 to 10 days

VI. Management

  1. See Fever Symptomatic Treatment
  2. See Fever Without Focus
  3. Fever is not harmful in critically ill patients (HEAT Trial)
    1. Lowering fever does not affect outcomes (including days admitted to ICU)
    2. Young (2015) N Engl J Med 373:2215-24 [PubMed]

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Ontology: Fever (C0015967)

Definition (CCC) Abnormal high body temperature
Definition (MEDLINEPLUS)

A fever is a body temperature that is higher than normal. It is not an illness. It is part of your body's defense against infection. Most bacteria and viruses that cause infections do well at the body's normal temperature (98.6 F). A slight fever can make it harder for them to survive. Fever also activates your body's immune system.

Infections cause most fevers. There can be many other causes, including

Treatment depends on the cause of your fever. Your health care provider may recommend using over-the-counter medicines such as acetaminophen or ibuprofen to lower a very high fever. Adults can also take aspirin, but children with fevers should not take aspirin. It is also important to drink enough liquids to prevent dehydration.

Definition (NCI_NCI-GLOSS) An increase in body temperature above normal (98.6 degrees F), usually caused by disease.
Definition (NCI_CTCAE) A disorder characterized by elevation of the body's temperature above the upper limit of normal.
Definition (NCI) Elevation of body temperature above normal due to inflammatory or immune responses.
Definition (NCI_NCI-GLOSS) Abnormally high body temperature. This may be caused as part of treatment, by an infection, or by exposure to heat.
Definition (NCI) A condition characterized by an abnormally high body temperature. In a hyperthermic state, the hypothalamic set-point is normal but body temperature increases and overrides the ability to lose heat, resulting from exogenous heat exposure or endogenous heat production.
Definition (NAN) Body temperature elevated above normal range
Definition (CSP) abnormal elevation of body temperature, usually as a result of a pathologic process.
Definition (MSH) An abnormal elevation of body temperature, usually as a result of a pathologic process.
Concepts Finding (T033)
MSH D005334
ICD9 780.60
ICD10 R50.9
SnomedCT 206762007, 274234009, 50177009, 64882008, 248425001, 158161008, 367493005, 248452006, 179260008, 386661006
LNC MTHU013245, MTHU013518, LA9540-1
English Fever, Fevers, Hyperthermia, Hyperthermias, Pyrexia, Pyrexias, PYREXIA, TEMPERATURE ELEVATION, Body temperature above normal, Fever, unspecified, [D]Fever NOS (context-dependent category), [D]Pyrexia (context-dependent category), [D]Fever NOS, High body temperature, Pyrexia [D], High temperature, febrile, fever, pyrexia, fever (physical finding), pyrexia (diagnosis), Elevated Core Body Temperature, Body temperature increased, Temperature elevation, Pyrexia NOS, Body temperature above reference range, Body temperature above normal (finding), Body temperature above reference range (finding), Fever NOS, Fever [Disease/Finding], rndx hyperthermia, rndx hyperthermia (diagnosis), increased body temperature, increases temperature, hyperthermic, fevered, Temperature;high, temperature increase, feverish, increase temperature, raised temperature, fevers, high body temperature, temperature elevation, elevated temperature, pyrexial, Pyrexia (finding), [D]Pyrexia (situation), Pyrexia [D] (situation), Increased body temperature (finding), Feels feverish, [D]Pyrexia, Hyperthermia (finding), [D]Fever NOS (situation), Feverish, FEVER, HYPERTHERMIA, hyperthermia, Increased body temperature, Febrile, Has a temperature, Temperature raised, Temperature elevated, Pyrexial, Fever (finding), febris, body temperature; increased, high; temperature, increased; body temperature, temperature; high, Hyperthermia - disorder, Hyperthermia [Ambiguous], Increased body temperature (finding) [Ambiguous], Pyrexia [D] (finding), high temperature
French FIEVRE, Elevation de la température corporelle, Température élevée, Pyrexie SAI, Fébrile, ELEVATION DE LA TEMPERATURE, PYREXIE, Fievreux, Température augmentée, Fièvre, Hyperthermie, Pyrexie
Portuguese FEBRE, PIREXIA, Temperatura alta, Elevação da temperatura, Pirexia NE, Febril, ELEVACAO DA TEMPERATURA, Doenças Febris, Enfermidades Febris, Temperatura corporal aumentada, Hipertemia, Febre, Pirexia, Hipertermia
Spanish FIEBRE, PIREXIA, Piréxico, Temperatura elevada, Pirexia NEOM, Elevación de temperatura, [D]pirexia (categoría dependiente del contexto), [D]fiebre, SAI (categoría dependiente del contexto), TEMPERATURA AUMENTADA, hipertermia, temperatura corporal por encima del rango de referencia (hallazgo), temperatura corporal por encima del rango de referencia, hipertermia (hallazgo), temperatura corporal aumentada, [D]fiebre, SAI (situación), aumento de la temperatura corporal (hallazgo), febril, temperatura corporal elevada, aumento de la temperatura corporal, pirexia (hallazgo), afiebrado, [D]pirexia (situación), [D]pirexia, [D]fiebre, SAI, Afiebrado, Enfermedades Febriles, fiebre (concepto no activo), fiebre (hallazgo), fiebre, pirexia, Temperatura corporal elevada, Fiebre, Pirexia, Hipertermia
German FIEBER, Temperatur hoch, fieberhaft, Temperaturanstieg, Pyrexie NNB, Fieber, nicht naeher bezeichnet, PYREXIE, TEMPERATURANSTIEG, Fieberhaft, Koerpertemperatur erhoeht, Fieber, Hyperpyrexie, Hyperthermie, Pyrexie
Italian Temperatura corporea aumentata, Febbrile, Piressia NAS, Temperatura elevata, Aumento della temperatura, Ipertermia, Piressia, Febbricitante, Febbre
Dutch koorts NAO, temperatuur stijging, hoge temperatuur, koorts, koortsig, koortsachtig, hoog; temperatuur, lichaamstemperatuur; verhoging, temperatuur; hoog, verhoging; lichaamstemperatuur, Koorts, niet gespecificeerd, hyperthermie, lichaamstemperatuur verhoogd, pyrexie, Koorts, Hyperthermie, Pyrexie
Japanese 発熱NOS, 高熱, 体温上昇, ハツネツNOS, コウタイオン, タイオンジョウショウ, コウネツ, ハツネツ, 高体温, 発熱, ネツッポイ, 熱っぽい, 熱病, 熱症状
Swedish Feber
Czech horečka, Pyrexie NOS, Pyretický, Zvýšení teploty, Hypertermie, Tělesná teplota zvýšená, Pyrexie, Horečka, Vysoká teplota, pyrexie, febrilní reakce, hypertermie
Finnish Kuume
Korean 상세불명의 열
Croatian VRUĆICA
Polish Gorączka
Hungarian Láz, Lázas, Testhőmérséklet emelkedett, Magas láz k.m.n., Hyperthermia, Pyrexia, Magas hőmérséklet, Hőmérséklet emelkedés
Norwegian Pyreksi, Feber, Hypertermi

Ontology: Relapsing Fever (C0035021)

Definition (MSH) An acute infection characterized by recurrent episodes of PYREXIA alternating with asymptomatic intervals of apparent recovery. This condition is caused by SPIROCHETES of the genus BORRELIA. It is transmitted by the BITES of either the body louse (PEDICULUS humanus corporis), for which humans are the reservoir, or by soft ticks of the genus ORNITHODOROS, for which rodents and other animals are the principal reservoirs.
Concepts Disease or Syndrome (T047)
MSH D012061
ICD9 087.9, 087
ICD10 A68.9 , A68
SnomedCT 46107006, 186822003, 186820006, 187374004, 420079008
LNC LA10500-9
English Fevers, Relapsing, Relapsing Fevers, Fever, Relapsing, Relapsing fever, unspecified, Relapsing fever,unspecified, [X]Relapsing fever, unspecified, [X]Relapsing fever,unspecified, relapsing fever, relapsing fever (diagnosis), Unspecified relapsing fever, Relapsing fever NOS, recurrent fever, Relapsing fevers, Relapsing Fever [Disease/Finding], fevers recurrent, Fever;relapsing, relapsing fevers, fever recurrent, fever relapsing, [X]Relapsing fever, unspecified (disorder), Relapsing fever NOS (disorder), febris; recurrens, fever; relapsing, relapsing; fever, Recurrent fever, NOS, Relapsing fever, NOS, Relapsing fever [dup] (disorder), Relapsing Fever, Relapsing fever, Recurrent fever due to Borrelia, Relapsing fever due to Borrelia, Recurrent fever, Relapsing fever (disorder)
Spanish fiebre recidivante (trastorno), fiebre recidivante, Fiebre recurrente no especificada, fiebre recidivante [dup] (trastorno), fiebre recurrente, SAI (trastorno), [X]fiebre recurrente, no especificada (trastorno), [X]fiebre recurrente, no especificada, fiebre recurrente, SAI, fiebre recidivante por Borrelia, fiebre recurrente por Borrelia, Fiebre recurrente, Fiebre Recurrente
Dutch niet-gespecificeerde febris recurrens, febris recurrens, niet-gespecificeerd, febris; recurrens, fever; relapsing, relapsing; fever, Febris recurrens, niet gespecificeerd, febris recurrens, Febris recurrens [Relapsing fever], Febris recurrens
French Fièvre récidivante non précisée, Fièvre récurrente, non précisée, Fièvre récurrente, Spirochétose récurrente
German unspezifisches Rueckfallfieber, Rueckfallfieber, unspezifisch, Rueckfallfieber, nicht naeher bezeichnet, Rueckfallfieber, Febris recurrens, Rückfallfieber
Italian Febbre ricorrente non specificata, Febbre ricorrente
Portuguese Febre recorrente NE, Febre recorrente, Febre Recorrente
Japanese 回帰熱, 詳細不明の回帰熱, 回帰熱、詳細不明, カイキネツショウサイフメイ, カイキネツ, ショウサイフメイノカイキネツ
Swedish Återfallsfeber
Czech návratná horečka, Blíže neurčená návratná horečka, Návratná horečka, blíže neurčená, Návratná horečka
Finnish Toisintokuume
Korean 재귀열, 상세불명의 재귀열
Polish Dur powrotny, Zakażenie Borrelia recurrentis, Gorączka powrotna
Hungarian visszatérő láz, Nem meghatározott visszatérő láz, Visszatérő láz, nem meghatározott
Norwegian Tilbakefallsfeber

Ontology: Continuous fever (C0424767)

Concepts Finding (T033)
SnomedCT 271751000
English sustained fever, sustained fever (physical finding), fever continuous, continuous fever, Continuous fever, Sustained fever, Continuous fever (finding)
Spanish fiebre continua (hallazgo), fiebre continua

Ontology: Fever, diurnal variation (C0424778)

Concepts Finding (T033)
SnomedCT 248445009
English Fever, diurnal variation, Fever, diurnal variation (finding)
Spanish fiebre, variación diurna (hallazgo), fiebre, variación diurna

Ontology: Fever, periodic, recurrent (C2675173)

Concepts Finding (T033)
English Fever, periodic, recurrent

Ontology: Fever, intermittent, recurrent (in some) (C3278593)

Concepts Finding (T033)
English Fever, intermittent, recurrent (in some)