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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Zaida Obeidat, M.D.

Synonyms and Keywords: Fever in kids


Historical Perspective


Body temperature °C °F
Normal 37-38°C 98.6-100.4°F
Mild/low grade fever 38.1-39°C 100.5-102.2°F
Moderate grade fever 39.1-40°C 102.2-104.0°F
High grade fever 40.1-41.1°C 104.1-106°F
Hyperpyrexia >41.1°C >106.0°F


The role of pyrogens and cryogens



The pathophysiological mechanisms for the injurious effects of a fever, classified as follows:[3]


Common conditions that can cause fevers include:

Fever in children can sometimes associated with more serious signs and symptoms, such as:

Serious bacterial infections include:

Causes of undiagnosed fever in children include:[4]

Differential diagnoses for fever in children

Cause Differential Diagnosis
Infectious; Bacterial or mycobacterial Brucellosis, dental abscess, endocarditis, non-tuberculous mycobacteria (eg, Mycobacterium chelonae), occult bacterial infection, recurrent bacterial infections, relapsing fever (Borrelia spp other than Borrelia burgdorferi), Yersinia enterocolitica
Parasitic Malaria (eg, Plasmodium vivax, Plasmodium ovale)
Inflammatory or Immunologic Behçet syndrome, inflammatory bowel disease (eg, Crohn disease), hereditary fever syndromes (eg, FMF), juvenile dermatomyositis, PFAPA syndrome, sarcoidosis, systemic lupus erythematous, systemic juvenile idiopathic arthritis (Still disease), vasculitis (eg, polyarteritis nodosa)
Malignant Leukemia, lymphoma
Other Benign giant lymph node hyperplasia (Castleman disease), CNS abnormalities (eg, hypothalamic dysfunction), drug fever, factitious fever, IgG4-related disease, immunodeficiency syndromes with recurrent infections

Epidemiology and Demographics


Natural History, Complications and Prognosis

  • Any abnormal increase body temperature in a child should be estimated as a potential symptom of an underlying condition.
  • Fever occurs when the body temperature increase by an alteration of the hypothalamic temperature set-point due to exposure to endogenous pyrogens.
  • Hyperthermia occurs when the body temperature increase due to failure of thermoregulation, whether by increased heat absorption, heat production and/or reduced ability to dissipate it.
  • Hyperthermia may have severe consequences on the body, since hyperthermia does not represent a controlled physiologic phenomenon.
  • Hyperthermia is less common in children, compared to fever.
  • Most cases of hyperthermia occurs due to environmental hyperthermia, caused by massive heat exposure, which overcomes the body’s thermoregulation, such as in the case of “forgotten baby syndrome” involving children left in cars during hot season.
  • Heat stroke is described as a core temperature ≥40 °C along with central nervous system dysfunction due to environmental heat exposure.
  • Young children have less efficient heat dissipation mechanisms, compared to older children and adults.
  • Other predisposing factors include:
    • Excessive fluids loss or that negatively affect water-electrolyte balance (e.g., gastrointestinal illness, diabetes insipidus, diabetes mellitus, cystic fibrosis, diuretics, fever)
    • Conditions associated with suboptimal sweating (spina bifida, familial dysautonomia, hypo/anhidrotic ectodermal dysplasia, Crisponi syndrome, Fabry disease)
    • Diminished thirst/water intake (cognitive impairment, young children)
    • Hypothalamic dysfunction
    • Anorexia nervosa
    • Obesity
  • Apart from environmental heat exposure, hyperthermia may be directly caused by conditions resulting in abnormal thermoregulation or increased heat production.
  • Central nervous system conditions involving injury to the hypothalamus (either congenital or acquired) may lead to temperature dysregulation and hyperthermia (sometimes called neurogenic or central fever).
  • Other causes include status epilepticus, thyrotoxicosis, and genetic syndromes associated with abnormal thermoregulation.
  • Intoxication from hyperthermia-inducing drugs may result in severe hyperthermia; involved drugs include stimulating/sympathomimetic drugs (cocaine, methamphetamine, MDMA), anticholinergic drugs (e.g., antihistamines, tricyclic antidepressants), serotoninergic drugs (serotonin syndrome), and salicylates
  • Neuroleptic malignant syndrome is a severe idiosyncratic reaction to antipsychotic agents, but also antiemetic agents such as metoclopramide, characterized by altered mental status, muscular rigidity, movement disorders, hyperthermia and autonomic dysfunction.
  • Malignant hyperthermia is a rare genetic disorder associated with several forms of congenital myopathy and triggered by succinylcholine or inhalational anesthetics agents; clinical features include rapid onset of extremely high temperature (38.5–46 °C), usually heralded by masseters spasm, muscle rigidity, metabolic acidosis, and hemodynamic collapse. Specific treatment, with discontinuation of involved anesthetics, muscular relaxation with sodium dantrolene, and correction of metabolic acidosis, has dramatically reduced the mortality, once as high as 70%, to less than 5%.

Fever is the most common reason for increased body temperature in pediatric clinical practice. The most common causes of fever in children are infections; non-infectious causes include immune-mediated, inflammatory, and neoplastic conditions. When a cause for fever cannot be identified by history and physical examination it is called “fever without source” (FWS). In industrialized countries, a minority of children with FWS will have a serious bacterial infection (SBI) (mainly urinary tract infection (UTI), less commonly pneumonia, sepsis, or meningitis), while the majority will have mild, self-resolving viral illnesses.

  • Signs and symptoms of a viral upper respiratory infection do not reliably exclude the possibility of an associated SBI, given the possibility of co-infections. In a study of children 2 to 36 months with FWS, at least one virus (most frequently adenovirus, human herpesvirus-6, enterovirus, and parechovirus) could be identified in 76% of children in whom no other explanation for the fever was found, but also in 40% of children with SBI. Therefore, detection of viral pathogens cannot be considered a discriminating factor.




Physical Examination

Laboratory Findings

Urinalysis and urine culture

  • Urinalysis is a key factor in the evaluation of fever in infancy and early childhood because UTI is a common cause of serious bacterial infection. *Urine sample should be obtained for all children younger than 24 months with unexplained fever. It may be obtained by catheterization or suprapubic aspiration.
  • In children with voluntary urine control, a clean catch method (urination into a specimen container after cleaning the area around the urethra) may be used.
  • Cultures of specimens collected in a urine bag may have an 85 percent false-positive rate, and urine dipstick testing has a 12 percent false-negative rate.
  • All specimens should be sent for formal urinalysis and culture.
  • UTI rates vary with patient sex and age.
  • In the first three months of life, UTIs are more common in boys than in girls, and much more common in uncircumcised boys. After three months of age, UTIs are more common in girls.

Blood cell counts and blood culture

  • White blood cell (WBC) counts and absolute neutrophil counts have been used to point out serious bacterial infection, including occult bacteremia.
  • Blood cell counts have higher value in neonates than in older children.
  • WBC counts lower than 5,000 per mm3 (5 × 109 per L) or more than 15,000 per mm3 (15 × 109 per L) had a PPV of 44% for serious bacterial infection, and an absolute neutrophil count of more than 10,000 per mm3 (10 × 109 per L) had a PPV of 71% according to a study of neonates up to 28 days of age.
  • Current guidelines recommend a complete blood count with differential and blood culture for infants three months or younger with fever.

Stool testing

  • Diarrhea with fever in neonates and young infants submit systemic illness therefore stool culture and fecal WBC counts are supported.

Inflammatory markers

  • The clinical value of C-reactive protein levels in recognizing serious infection in neonates, infants, and young children is being explored.
  • C-reactive protein (CRP) level of 2 mg per dL (19 nmol per L) or greater has better sensitivity, specificity, and predictive value than a WBC count of greater than 15,000 per mm3 or less than 5,000 per mm3.
  • Elevated levels of procalcitonin (another marker of inflammation and bacterial infection) also appear to have better sensitivity, specificity, and predictive value than WBC counts.

Lumbar puncture

  • Vaccination against S. pneumoniae and Hib has greatly reduced the incidence of meningitis limiting the need for lumbar puncture.
  • Fever with clinical signs of meningitis such as nuchal rigidity, petechiae, or abnormal neurologic findings in neonates, infants and young children is indication for lumbar puncture.
  • In children older than 3 months, the test is not suggested unless neurologic signs are present.
  • Two guidelines recommended a lumbar puncture for well-appearing, previously healthy young infants with no focal signs of infection, a WBC count between 5,000 and 15,000 per mm3, and no pyuria or bacteriuria on urinalysis.
  • Although low peripheral WBC counts (less than 5,000 per mm3) are more often associated with meningitis than with bacteremia, WBC counts should not be used alone to determine which infants need lumbar puncture.


There are no ECG findings associated with fever in children.


  • Chest X ray is recommended in all neonates with unexplained fever.
  • Chest X ray is also recommended for young children older than one month revealing respiratory symptoms and for patients with a fever of more than 102.2°F (39°C) and a WBC count of more than 20,000 per mm3 (20 × 109 per L).

Echocardiography or Ultrasound

There are no echocardiography/ultrasound findings associated with fever in children.

CT scan

There are no CT scan findings associated with fever in children.


There are no MRI findings associated with fever in children.


Medical Therapy

  • Fever plays a physiologic role in response to infection, inhibiting bacterial growth and viral replication, and enhancing the immune response.
  • There is no evidence that use of antipyretics prolongs illness in children
  • Antipyretic treatment should be reserved for distressed children, aiming at improving the child’s wellbeing rather than achieving normothermia.
  • Antipyretic treatment has not been shown to prevent recurrence of febrile seizures.
  • Response to antipyretics cannot predict the severity of the underlying illness, since children with bacterial and viral illnesses have a similar response to antipyretics [134]. However, evaluating if the child’s conditions markedly improve with antipyretic treatment may be useful to discern whether it was related to fever or to the severity of the underlying illness.
  • In children with inherited metabolic and mitochondrial diseases, catabolic stressors should be avoided, and both fever and underlying infections should be treated
  • Fever may increase metabolic and oxygen consumption; therefore, aggressive treatment may be more important in children with a limited cardiopulmonary or metabolic reserve, and it is recommended in patients recovering from cardiac arrest.
  • Ibuprofen and acetaminophen are the only drugs approved for treatment of fever in children and they are generally considered to be equally safe and effective for reducing temperature and relieving discomfort.
  • Combination therapy with acetaminophen plus ibuprofen seems to be slightly more effective in reducing body temperature compared with monotherapy alone[7]


  1. Stein MT (1991). "Historical perspective on fever and thermometry". Clin Pediatr (Phila). 30 (4 Suppl): 5–7. doi:10.1177/0009922891030004S02. PMID 2029820.
  2. 2.0 2.1 2.2 Ogoina D (2011). "Fever, fever patterns and diseases called 'fever'--a review". J Infect Public Health. 4 (3): 108–24. doi:10.1016/j.jiph.2011.05.002. PMID 21843857.
  3. Walter EJ, Hanna-Jumma S, Carraretto M, Forni L (2016). "The pathophysiological basis and consequences of fever". Crit Care. 20 (1): 200. doi:10.1186/s13054-016-1375-5. PMC 4944485. PMID 27411542.
  4. BREWIS EG (1965). "CHILD CARE IN GENERAL PRACTICE. UNDIAGNOSED FEVER". Br Med J. 1 (5427): 107–9. PMC 2165027. PMID 14218464.
  5. Soon GS, Laxer RM (2017). "Approach to recurrent fever in childhood". Can Fam Physician. 63 (10): 756–762. PMC 5638471. PMID 29025800.
  6. Van den Bruel A, Haj-Hassan T, Thompson M, Buntinx F, Mant D, European Research Network on Recognising Serious Infection investigators (2010). "Diagnostic value of clinical features at presentation to identify serious infection in children in developed countries: a systematic review". Lancet. 375 (9717): 834–45. doi:10.1016/S0140-6736(09)62000-6. PMID 20132979.
  7. Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS (2017). "Fever in Children: Pearls and Pitfalls". Children (Basel). 4 (9). doi:10.3390/children4090081. PMC 5615271. PMID 28862659.