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 Fever in Infants and Children: A Merck Manual of Patient Symptoms podcast
Normal body temperature varies from person to person and throughout the day, but fever usually is defined as a core body (rectal) temperature ≥ 38.0° C.
Significance of fever depends on clinical context rather than peak temperature; some minor illnesses cause high fever, whereas some serious illnesses cause only a mild temperature elevation. Although parental assessment is frequently clouded by fear of fever, the history of a temperature taken at home should be considered equivalent to a temperature taken in the office.
Pathophysiology
Normal body temperature varies during the day by as much as 0.5° C and, in a child with a febrile illness, by as much as 1.0° C.
Fever occurs in response to the release of endogenous pyogenic mediators called cytokines. Cytokines stimulate the production of prostaglandins by the hypothalamus, which readjust and elevate the temperature set point (see Biology of Infectious Disease: Fever).
Fever plays an integral role in fighting infection and, although it is uncomfortable, does not necessitate treatment in an otherwise healthy child. Some studies even indicate that lowering the temperature can prolong some illnesses. However, fever increases the metabolic rate and the demands on the cardiopulmonary system. Therefore, fever can be detrimental to children with pulmonary or cardiac compromise or neurologic impairment. It can also be the catalyst for febrile seizures, a typically benign childhood condition (see see Neurologic Disorders in Children: Febrile Seizures).
Etiology
Causes of fever (see Table 20: Approach to the Care of Normal Infants and Children: Some Common Causes of Fever in Children* ) differ based on whether the fever is acute (≤ 7 days ) or chronic (> 7 days). Response to antipyretics and height of the temperature have no direct relationship to the etiology or its seriousness.
Acute:
Most acute fevers in infants and young children are caused by infection. The most common are
However, potential causes vary with the child's age. Causes vary because neonates (infants < 28 days) and young infants have decreased immunologic function and are therefore at greater risk of infection and because neonates may have perinatally acquired infection. Common perinatal infections include those with group B streptococci, Escherichia coli, Listeria monocytogenes, and herpes simplex virus; these organisms can cause bacteremia, pneumonia, meningitis, or sepsis.
Febrile children < 36 mo are at special risk of occult bacteremia (pathogenic bacteria in the bloodstream but without focal symptoms or signs). The most common causative organisms of occult bacteremia used to be Streptococcus pneumoniae and Haemophilus influenzae; vaccination against both is now widespread in the US and Europe, making occult bacteremia less common and potentially changing the common causative organisms.
Rare, noninfectious causes of acute fevers include heatstroke and toxic ingestions (eg, of drugs with anticholinergic effects). Some vaccinations can cause fever for days (eg, with pertussis vaccination) and even 1 or 2 wk (eg, with measles vaccination) after administration. These fevers typically last from a few hours to a day. If the child is otherwise well, no evaluation is necessary. Teething does not cause fever.
Chronic:
Chronic fever suggests various potential causes, including autoimmune disorders, collagen vascular diseases (eg, juvenile idiopathic arthritis, inflammatory bowel disease), cancer (eg, leukemia, lymphoma), and chronic infections (eg, osteomyelitis, TB). Miscellaneous causes include factitious fever and cases in which etiology is not identified.
The most common causes include
Collagen vascular diseases, autoimmune disorders, and cancer are much less common.
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Table 20
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| Some Common Causes of Fever in Children* |
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Type
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Examples
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Acute
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Infectious†
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Viral infection (eg, respiratory syncytial virus, parainfluenza, adenovirus, influenza, rotavirus, enterovirus)
Otitis media
Streptococcal infections (eg, pharyngitis, scarlet fever, impetigo)
UTI or pyelonephritis
Occult bacteremia (in infants < 36 mo)
Pneumonia
Enteritis
Bone and joint infections
Cellulitis or other soft-tissue infections
Viral encephalitis
Meningitis (uncommon)
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Noninfectious
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Heatstroke
Nervous system dysfunction
Toxic ingestions
Vaccines
Drugs
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Chronic
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Infectious‡
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Viral infections (eg, Epstein-Barr virus, cytomegalovirus, hepatitis virus, arboviruses)
Sinusitis
Abscesses (intra-abdominal, hepatic, nephric)
Bone and joint infections (eg, osteomyelitis, septic arthritis)
Endocarditis
HIV infection (uncommon)
TB (uncommon)
Parasitic infections (eg, malaria—uncommon)
Lyme disease (rarely causes chronic fever)
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Noninfectious
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Inflammatory bowel disease
Rheumatoid disorders
Cancer
Drugs
Factitious fever
Hyperthyroidism
Familial hereditary disorders
Granulomatous diseases (rare)
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*Causes are listed from the most to the least common.
†Neonates (≤ 28 days) are susceptible to perinatally acquired organisms: group B streptococci, Escherichia coli, Listeria monocytogenes, and herpes simplex viruses.
‡There are many infectious causes of chronic fever. This list is not exhaustive.
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Evaluation
History:
History of present illness should note degree and duration of fever, method of measurement, and the dose and frequency of antipyretics (if any). Important associated symptoms that suggest serious illness include poor appetite, irritability, lethargy, and change in crying (eg, duration, character). Associated symptoms that may suggest the cause include vomiting, diarrhea (including presence of blood or mucus), cough, difficulty breathing, favoring of an extremity or joint, and strong or foul-smelling urine. Drug history should be reviewed for indications of drug-induced fever.
Factors that predispose to infection are identified. In neonates, these factors include prematurity, prolonged rupture of membranes, maternal fever, and positive prenatal tests (usually for group B streptococcal infections, cytomegalovirus infections, or sexually transmitted diseases). For all children, predisposing factors include recent exposures to infection (including family and caretaker infection), indwelling medical devices (eg, catheters, ventriculoperitoneal shunts), recent surgery, and travel and environmental exposures (eg, to ticks, mosquitoes, cats, farm animals, or reptiles).
Review of systems should note symptoms suggesting possible causes, including runny nose and congestion (viral URI), headache (sinusitis, Lyme disease, meningitis), ear pain or waking in the night with signs of discomfort (otitis media), cough or wheezing (pneumonia, bronchiolitis), abdominal pain (pneumonia, gastroenteritis, UTI, abdominal abscess), back pain (pyelonephritis), and any history of joint swelling or redness (Lyme disease, osteomyelitis). A history of repeated infections (immunodeficiency) or symptoms that suggest a chronic illness, such as poor weight gain or weight loss (TB, cancer), is identified. Certain symptoms can help direct the evaluation toward noninfectious causes; they include heart palpitations, sweating, and heat intolerance (hyperthyroidism) and recurrent or cyclic symptoms (a rheumatoid, inflammatory, or hereditary disorder).
Past medical history should note previous fevers or infections and known conditions predisposing to infection (eg, congenital heart disease, sickle cell anemia, cancer, immunodeficiency). A family history of an autoimmune disorder or other hereditary conditions (eg, familial dysautonomia, familial Mediterranean fever) is sought. Vaccination history is reviewed to identify patients at risk of infections that can be prevented by a vaccine.
Physical examination:
Vital signs are reviewed, noting abnormalities in temperature and respiratory rate. In ill-appearing children, BP should also be measured. Temperature should be measured rectally in infants for accuracy. Any child with cough, tachypnea, or labored breathing requires pulse oximetry.
The child's overall appearance and response to the examination are important. A febrile child who is overly compliant or listless is of more concern than one who is uncooperative. However, an irritable infant or child who is inconsolable is also of concern. The febrile child who looks quite ill, especially when the temperature has come down, is of great concern and requires in-depth evaluation and continued observation. However, children who appear more comfortable after antipyretic therapy do not always have a benign disorder.
The examination seeks signs of causative disorders (see Table 21: Approach to the Care of Normal Infants and Children: Examination of the Febrile Child).
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Table 21
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| Examination of the Febrile Child |
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Area
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Finding
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Possible Cause
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Abdomen
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Tenderness, distention
Absent bowel sounds
Mass
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Gastroenteritis
Abdominal abscess
Tumor
Appendicitis
Pyelonephritis
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Extremities
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Joint swelling, erythema, tenderness
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Septic arthritis (very tender)
Lyme arthritis
Rheumatoid or inflammatory disorder
Osteomyelitis
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Fontanelle (infants)
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Bulging
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Meningitis or encephalitis
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General appearance
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Listless, weak response to aversive stimuli (eg, otoscopy) or, conversely, exaggerated response to stimuli and difficulty consoling
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Meningitis or encephalitis
Sepsis
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Lungs
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Coughing, tachypnea, crackles, rhonchi, decreased breath sounds, wheezing
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Lower respiratory infection (eg, pneumonia, bronchiolitis, pulmonary foreign body)
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Neck
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Adenopathy, with or without redness and tenderness
Pain or resistance to flexion (meningismus*)
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Upper respiratory viral infection
Lymphadenitis
Epstein-Barr virus infection
Cat-scratch disease
Lymphoreticular cancer (rare)
Meningitis
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Nose
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Congestion, discharge
Nostril flaring with inspiration
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URI
Sinusitis
Lower respiratory infection
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Pharynx
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Redness
Sometimes exudate or swelling
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Pharyngitis (URI or strep infection)
Retropharyngeal abscess
Tonsillitis
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Skin
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Petechiae
Purpura
Atypical ecchymoses
Lacelike maculopapular rash on trunk and extremities with slapped-cheek appearance
Focal erythema with swelling
Evanescent erythematous morbilliform rash on trunk and proximal extremities
Bull's-eye erythematous rash, single or multiple lesions
Erythematous, sandpaper-like rash
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Blood dyscrasia due to sepsis
Cancer
Drug reactions
Erythema infectiosum (fifth disease, which is caused by parvovirus B19)
Cellulitis
Skin abscess
Juvenile idiopathic arthritis
Lyme disease
Scarlet fever (group A streptococcal infection)
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Tympanic membranes
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Red, bulging membrane, loss of landmarks
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Otitis media
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*Meningismus is not consistently present in children < 2 yr with meningitis.
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Red flags:
The following findings are of particular concern:
Interpretation of findings:
Although serious illness does not always cause high fever, and many high fevers result from self-limited viral infections, a temperature of ≥ 39° C in children < 3 yr indicates higher risk of occult bacteremia.
Acute fever is infectious in most cases, and of these, most are viral. History and examination are adequate to make a diagnosis in older children who are otherwise well and not toxic-appearing. Typically, they have a viral respiratory illness (recent ill contact, runny nose, wheeze, or cough) or GI illness (ill contact, diarrhea, and vomiting). Other findings also suggest specific causes (see Table 21: Approach to the Care of Normal Infants and Children: Examination of the Febrile Child).
However in infants < 36 mo, the possibility of occult bacteremia, plus the frequent absence of focal findings in neonates and young infants with serious bacterial infection, necessitates a different approach. Evaluation varies by age group. Accepted categories are neonates (≤ 28 days), young infants (1 to 3 mo), and older infants and children (3 to 36 mo). Regardless of clinical findings, a neonate with fever requires immediate hospitalization and testing to rule out a dangerous infection. Young infants may require hospitalization depending on screening laboratory results and the likelihood that they will be brought in for follow-up.
Chronic fever requires a high index of suspicion for the many potential causes. However, certain findings can suggest the disorder: erythema chronicum migrans rash, intermittent joint swelling, and neck pain (Lyme disease); intermittent headaches with runny nose or congestion (sinusitis); weight loss, high-risk exposure, and night sweats (TB); weight loss or difficulty gaining weight, heart palpitations, and sweating (hyperthyroidism); and weight loss, anorexia, and night sweats (cancer). Certain conditions (eg, granulomatous diseases) may manifest with nonspecific symptoms and a history that involves repeated infections (eg, pneumonia, skin infections, abscesses, septicemia).
Testing:
Testing depends on whether fever is acute or chronic.
For acute fever, testing for infectious causes is directed by the age of the child (see Fig. 1: Miscellaneous Infections in Infants and Children: Evaluation and management of the febrile infant aged < 3 mo. and Fig. 2: Miscellaneous Infections in Infants and Children: Fever in children aged 3 to 36 mo.).
All febrile children < 3 mo require a WBC count with a manual differential, blood cultures, and urinalysis and urine culture (urine obtained by catheterization, not an external bag). Lumbar puncture is mandatory for children < 28 days; expert opinion varies about the need for the test in children aged 29 days to 2 mo. Chest x-ray, stool swabs for WBCs, stool cultures, and acute-phase reactant tests (eg, ESR, C-reactive protein) are done depending on symptoms and degree of suspicion.
Febrile children between 3 mo and 36 mo who look well and can be watched carefully do not require laboratory testing. If the child has symptoms or signs of specific infections, clinicians should order appropriate tests (eg, chest x-ray when there is hypoxemia, dyspnea, or grunting; urinalysis and culture when there is foul-smelling urine; lumbar puncture when there is abnormal behavior or meningismus). If the child looks ill or has a temperature > 39° C but has no localizing signs, blood counts and cultures and urine tests should be considered as well as a lumbar puncture.
For febrile children > 36 mo, testing should be directed by history and examination; screening blood cultures and WBC counts are not indicated.
For chronic fever, testing for noninfectious causes should be directed by history, physical examination, and suspected disorder (eg, thyroid-stimulating hormone [TSH] and thyroxine [T4] for suspected hyperthyroidism; antinuclear antibodies and Rh factor for suspected juvenile idiopathic arthritis).
Children without focal findings should have initial screening tests, including
An elevated ESR suggests inflammation (infection, TB, autoimmune disorder, cancer), and further testing can be done. If the WBC count is normal, indolent infection is less likely; however, if infection is suspected clinically, serologic testing for possible causes (eg, Lyme disease, cat-scratch disease, mononucleosis, cytomegalovirus) can be done, as well as blood cultures. Imaging tests can be helpful in detecting tumors, collections of purulent material, or osteomyelitis. The type of test is determined by the specific concern. For example, head CT is used for diagnosis of sinusitis; both CT and MRI are used for identification of a tumor and metastatic lesions, and bone scanning is used for detection of osteomyelitis. Bone marrow aspiration can be done to detect cancers such as leukemia.
Treatment
Treatment is directed at the underlying disorder.
Fever in an otherwise healthy child does not necessarily require treatment. Although antipyretics can provide comfort, they do not change the course of an infection. In fact, fever is an integral part of the inflammatory response to infection and can help the child fight the infection. However, most clinicians use antipyretics to help alleviate discomfort and to reduce physiologic stresses in children who have cardiopulmonary disorders, neurologic disorders, or a history of febrile seizures.
Antipyretic drugs that are typically used include
Acetaminophen tends to be preferred because ibuprofen decreases the protective effect of prostaglandins in the stomach and, if used chronically, can lead to gastritis. The dosage of acetaminophen is 10 to 15 mg/kg po or rectally q 4 to 6 h. Ibuprofen dosage is 10 mg/kg po q 6 h. Use of one antipyretic at a time is preferred; however, some clinicians alternate the 2 drugs to treat high fever (eg, acetaminophen at 6 AM, 12 PM, and 6 PM and ibuprofen at 9 AM, 3 PM, and 9 PM). This approach is not encouraged because caregivers may become confused and inadvertently exceed the recommended daily dose. Aspirin should be avoided because it increases the risk of Reye's syndrome (see see Miscellaneous Disorders in Infants and Children: Reye's Syndrome) if certain viral illnesses such as influenza and varicella are present.
Nondrug approaches to fever include putting the child in a warm or tepid bath, using cool compresses, and undressing the child. Caregivers should be cautioned not to use a cold water bath, which is uncomfortable and, by inducing shivering, may paradoxically elevate body temperature. As long as the temperature of the water is slightly cooler than the temperature of the child, a bath provides temporary relief.
Things to avoid:
Wiping the body down with isopropyl alcohol should be strongly discouraged because alcohol can be absorbed through the skin and cause toxicity. Numerous folk remedies exist, ranging from the harmless (eg, putting onions or potatoes in socks) to the uncomfortable (eg, coining, cupping).
Key Points
Last full review/revision February 2010 by Eve R. Colson, MD; Rachel L. Chapman, MD; Melissa R. Held, MD
Content last modified February 2010
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