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Normal body temperature varies from person to person and throughout the day. As a working standard, fever is defined as a core body (rectal) temperature ≥ 38.0° C. Significance of fever depends on clinical context; some minor illnesses cause high fevers while some serious illnesses cause only mild temperature elevations.
Etiology
Nearly all acute fevers in infants and young children are caused by infection, most commonly viral respiratory or GI illness. Bacterial infections, typically otitis media, pneumonia, and UTI, are less common but occasionally very serious (eg, meningitis). Infants < 28 days are susceptible to perinatally acquired infection with group B Streptococcus, Escherichia coli, Listeria monocytogenes, and herpes simplex virus.
Children < 2 yr (particularly infants ≤ 3 mo) are at special risk of occult bacteremia (see Infections in Infants and Children: Occult Bacteremia), defined as the presence of pathogenic bacteria in the blood of a febrile child who has no focal signs or symptoms. The most common causative organisms are Streptococcus pneumoniae and Haemophilus influenzae; vaccination against both of these is now widespread in the US and Europe, making occult bacteremia less common.
Rare, noninfectious causes of acute fevers include heat stroke and toxic ingestions (eg, anticholinergic agents). Some vaccinations can cause fever days (eg, pertussis) and even 1 or 2 wk (eg, measles) 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 fever suggests various potential causes, ranging from autoimmune disease (eg, juvenile RA, inflammatory bowel disease) to cancer (eg, leukemia, lymphoma), as well as chronic infections (eg, osteomyelitis, UTI). Hereditary periodic fevers are reviewed in Hereditary Periodic Fever Syndromes.
Evaluation
Evaluation varies by age group and focuses on identifying a source for infection or underlying noninfectious condition. Acute fever in an infant ≤ 3 mo requires a thorough evaluation regardless of other signs and symptoms because serious infection (eg, sepsis, meningitis) may occur without other manifestations.
History:
For infants < 3 mo, history should focus on risks for sepsis, including maternal infection, prematurity, recent surgery, or known conditions such as HIV infection. In older children, history should focus on localizing symptoms and signs, vaccination history, recent exposures to infection (including family and caretaker infection), and other risk factors for infection, including indwelling medical devices (eg, catheters, ventriculoperitoneal shunts) and conditions predisposing to infection (eg, congenital heart disease, sickle cell anemia, neoplasm, immunodeficiency). A family history of autoimmune disease is relevant. Although there is no direct correlation between the height of fever and the seriousness of the cause, a temperature of 39°C puts children < 2 yr at higher risk for having occult bacteremia.
Physical examination:
Appraisal of the child's overall appearance is critical. The febrile child who looks quite ill, especially when the temperature has come down, is a source of great concern and requires in-depth evaluation and continued observation. In all febrile children, careful attention should be paid to the tympanic membranes, throat, chest, abdomen, lymph nodes, neck flexibility, and skin. Petechiae or purpura often indicates serious infection.
Testing:
All febrile children < 3 mo require WBC testing with a manual differential, blood cultures, and urinalysis and urine culture. Lumbar puncture is mandatory for children < 2 mo; opinions vary about the need for the test in children between 2 mo and 3 mo. Many providers also obtain a chest x-ray, and some obtain stool swabs for WBCs and stool cultures. Some clinicians add acute-phase reactants (eg, ESR, C-reactive protein, procalcitonin); however, although abnormalities on these tests are more common in serious bacterial illness, sensitivities and specificities are low, and use of these tests is under debate.
Febrile children between 3 mo and 24 mo who look well and can be watched carefully do not necessarily require laboratory testing. If there are signs or symptoms of specific infections, appropriate tests should be ordered (eg, chest x-ray when there is hypoxemia, dyspnea, or grunting; urinalysis and culture when there is foul-smelling urine). If the child looks ill but has no localizing signs, blood counts and cultures and urine tests should be considered as well as a lumbar puncture.
Testing in children > 24 mo is dictated by history and examination; screening blood cultures and WBC counts are not indicated.
Treatment
Symptomatic treatment of fever typically includes acetaminophen 10 to 15 mg/kg po or per rectum q 4 to 6 h (not to exceed 5 doses in 24 h) or ibuprofen 5 to 10 mg/kg q 6 to 8 h.
Definitive treatment of a clearly identified infection is site-specific. Management of fever without a clear source is determined by age, history, and screening test results.
Most experts treat infants ≤ 28 days with hospital admission and IV antibiotics to cover neonatal and community-acquired pathogens until results of screening tests are available. Current recommendations are for ceftriaxone (50 to 75 mg/kg q 24 h or 80 to 100 mg/kg q 24 h if cells are present in CSF) or cefotaxime (50 mg/kg q 6 h) plus ampicillin to cover Listeria and Enterococcus. Vancomycin (15 mg/kg q 6 h) can be added if penicillin-resistant Streptococcus pneumoniae is suspected, and acyclovir (20 mg/kg q 8 h) when herpes simplex is likely.
Criteria for managing febrile children between 3 and 24 mo are changing because of the effectiveness of vaccination on decreasing the incidence of occult bacteremia. Decisions about how intensive the testing should be, whether the child should receive antibiotics while cultures are pending, and whether management is conducted in the hospital or as an outpatient depend on the child's overall appearance, the family's reliability, and the presence or absence of risk factors for occult bacteremia. For detailed recommendations, see Fig. 2: Infections in Infants and Children: Evaluation and management of the febrile child aged 3 to 36 mo. .
Children > 24 mo require only symptomatic treatment.
Last full review/revision November 2005
Content last modified November 2005
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