Fever

Although fever is a normal physiologic response to a bacterial, viral, or immunologic process, it is a common concern among parents and reason for seeking medical care. In this section, we review evaluation and management of fever in children older than 60 days.

Other topics related to fever management are covered in the following rotation guides:

• Fever in Young Infants (Pediatric Emergency Medicine)

• Febrile Seizures (Pediatric Neurology)

• The Ill or Lethargic Infant (Pediatric Emergency Medicine)

Measurement of Body Temperature

Normal body temperature, defined by Carl Wunderlich in 1868, is 37.0°C (98.6°F), with a range between 36.2°C (97.2°F) and 37.5°C (99.5°F). Fever is defined as a temperature at or above 38.0°C (100.4°F).

Temperature measurements vary depending on the type of thermometer utilized: axillary, oral, rectal, or infrared. A rectal temperature is the preferred and most accurate method for evaluating fever in an infant. Oral and axillary temperatures can also be used, depending on the child’s age and level of cooperation.

Evaluation of fever in the pediatric population depends on patient age and risk stratification. Many institutions utilize their own evidence-based clinical guidelines in the evaluation of well-appearing infants and young children with fever and no localizing signs. Variation also exists among institutions regarding specific recommendations for evaluating for occult infection.

Ill-appearing (lethargic, pale, poor feeding) patients should undergo lab evaluation based on clinical exam findings. Special consideration for Kawasaki disease should be entertained in patients with fever for ≥5 days. Multisystem inflammatory syndrome in children (MIS-C) is an inflammatory disease associated with SARS-CoV-2 infection that may also present with persistent fever. Patients with fever of unknown origin (>8 days) may require additional testing based on history and exam findings.

Evaluation of Fever by Age

Neonates and Young Infants (<2 Months)

See the Pediatric Emergency Medicine rotation guide.

Age 2-6 Months

At age 2-6 months, development of motor, social, and communication skills helps the physician make a clinical judgment about the “wellness” of a patient with fever. However, well-appearing infants in this age group are at risk of harboring serious bacterial infection (SBI) due to partially vaccinated status, even though bacterial meningitis is rare in low-risk patients. Therefore, accurate vaccination history is critical in determining the appropriate workup.

Vaccinations have dramatically changed standards of care for the evaluation of fever at ages 2−6 months. The effects of the Haemophilus influenzae type b (Hib) vaccine, introduced in 1985, followed by the 7-valent pneumococcal conjugate vaccine (PCV7), in 2000, led to dramatic reductions in the incidence of invasive disease. When the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced, in 2010, preliminary studies showed an even larger decrease in invasive disease in children after two doses. The risk for SBI decreases with number of doses of Hib and pneumococcal vaccines. Children who have been adequately vaccinated have lower risk of developing an invasive bacterial illness from these potentially serious organisms, and therefore less of an indication for blood cultures and complete blood count.

Immunogenicity increases with each dose of vaccine, and in well-appearing children who have received two to three doses of Hib and pneumococcal vaccines, incidence of bacteremia is low. Management of fever in this age group is aimed at using evidence-based screening to determine which patients are at low risk for SBI. Although the specifics of clinical guidelines vary among institutions, there is consensus that in this age group, patients do not necessarily need blood tests if they have a well-defined viral illness (e.g., stomatitis) or identifiable bacterial illness (e.g., otitis media, pneumonia) or another condition known to cause fever (e.g., vaccination). In infants with high fever and no identifiable source of infection, urine evaluation for urinary tract infection (UTI) should be considered. Females and uncircumcised males are at highest risk for UTI. Many institutions use a temperature of 38.5°C to 39.0°C (101.3°F to 102.2°F) as a threshold for further evaluation for SBI in this age group.

Studies in infants younger than 3 months indicate that the inflammatory marker C-reactive protein (CRP) and the sepsis biomarker procalcitonin are useful in detecting SBI. However, these tests have not been well studied in patients ages 3−6 months.

Age 6-24 Months

In this age group, many children will have a viral illness or identifiable bacterial source of infection as a cause of their fever. Fully vaccinated children aged 6−24 months who are well appearing likely do not need blood tests. Nonvaccinated children, or those who have received less than three doses of pneumococcal vaccine are at somewhat higher risk of developing bacteremia or meningitis. Recommendations are more conservative for nonvaccinated infants in this age group due to the higher risk of developing SBI.

The following tests may be indicated in the evaluation of fever in children ages 6−24 months:

• Chest radiograph may be considered in children with respiratory symptoms that suggest a lower respiratory infection. Occult pneumonia is a concern in infants with high fever and elevated leukocyte count. Although the most common cause of community-acquired pneumonia is viral pneumonia, the most common bacterial cause of community-acquired pneumonia continues to be Streptococcus pneumoniae. Although incidence of pneumococcal pneumonia is decreasing with increased vaccination rates, nonvaccinated children and younger infants may not have received sufficient doses of the vaccine to be protected. See the Pediatric Infectious Diseases rotation guide for further information on pneumonia.

• Urinalysis is often indicated depending on patient age and risk factors. In vaccinated children in this age group, Escherichia coli is a common cause of bacteremia and is often associated with urinary tract infection. Research has shown that even in cases of confirmed viral illness (e.g., respiratory syncytial virus [RSV], bronchiolitis, and influenza), UTI remains a clinical concern. See the Pediatric Emergency Medicine and Pediatric Nephrology rotation guides for more detailed information on UTI and risk factors.

Fever Reduction

The two most commonly used medications to reduce fever in the United States are ibuprofen and acetaminophen.

• Ibuprofen is sold in two concentrations: infant (50 mg per 1.25 mL) or children (100 mg per 5 mL). It is essential to explain to caregivers the importance of giving the correct concentration and dose. Ibuprofen should not be given to children younger than 6 months because of the risk of adverse gastrointestinal effects and risk of renal failure due to immature renal function.

• Acetaminophen is sold in one concentration (160 mg per 5 mL), regardless of whether it is for infants or children. Rectal formulations can be helpful in children who are vomiting.

Note: Aspirin should not be given to children to treat fever because of the serious risk of developing Reye syndrome.

A sponge bath is a nonpharmacologic option for reducing fever in a child. This method can be helpful if a child is vomiting or has a rare allergy to antipyretics. It is important to use lukewarm water and avoid using cold water because it may cause shivering and further increase the body temperature.