Fever in the Older Child

Viral Infections

Viral infections are the most common cause of fever, and the prevalence of specific viral infections varies by season. In the summer and early fall, enteroviruses (e.g., coxsackieviruses) predominate, usually presenting as hand-foot-and-mouth disease, herpangina, aseptic meningitis, or a variety of other manifestations. In the late fall and winter, viral upper and lower respiratory tract infections such as respiratory syncytial virus (RSV) and influenza and gastrointestinal (GI) viruses such as norovirus and rotavirus are common. Parainfluenza virus is a common cause of laryngotracheobronchitis (croup) and occurs primarily in the fall and spring, affecting mostly infants and toddlers. Varicella is a less common cause of fever than in the past because of childhood vaccination but still occurs, with the highest incidence in winter and early spring.

Bacterial Infections

Although viral infections are the most common cause of fever in older infants and children and are often diagnosed based on symptoms and physical examination findings, bacterial infections also occur. Common bacterial infections include acute otitis media and streptococcal pharyngitis (strep throat) . Acute otitis media is diagnosed by the presence of a bulging, erythematous, and nonmobile tympanic membrane upon insufflation. Strep throat occurs most frequently in the late fall and winter and is uncommon before age 3 yr. The presence of focal auscultatory findings, including crackles, is suggestive of a lower respiratory tract infection, such as bacterial pneumonia, but may also be present among children with bronchiolitis . Atypical pneumonia caused by mycoplasma typically occurs in school-age children and is often associated with headache, malaise, and low-grade fever. The presence of neck pain or drooling may indicate a deep neck infection such as a retropharyngeal abscess , which occurs in infants and young children, or a peritonsillar abscess , which typically affects older children. Skin and soft tissue infections such as cellulitis and abscess may also present with fever, with the buttock a common area for abscesses in young children. Bone and joint infections such as osteomyelitis and septic arthritis may present with fever and refusal to bear weight or limp in the young child. Invasive bacterial infections, including sepsis and bacterial meningitis , must be considered in young children presenting with fever. While uncommon, these infections are potentially life-threatening and require prompt recognition and treatment. Ill appearance, lethargy, and tachycardia are typically present among children with severe sepsis, and petechiae may be an early finding among children with meningococcemia or other invasive bacterial diseases. Figs. 203.1 and 203.2 show age-related diagnoses and organisms producing bacterial sepsis in infants and children. Children with fever who are immunosuppressed, such as children receiving chemotherapy or those with sickle cell disease, are at higher risk for invasive bacterial infection.

Infants and children age 2-24 mo merit special consideration because they have limited verbal skills, are at risk for occult bacterial infections, and may be otherwise asymptomatic except for fever (see Chapter 202 ).

Occult Urinary Tract Infection

Among children 2-24 mo old without symptoms or physical examination findings that identify another focal source of infection, the prevalence of urinary tract infection (UTI) may be as high as 5–10%. The highest risk of UTI occurs in females and uncircumcised males, with a very low rate of infection (<0.5%) in circumcised males. Table 203.2 lists risk factors for UTI.

Occult Bacteremia

Occult bacteremia is defined as a positive blood culture for a pathogen in a well-appearing child without an obvious source of infection. In the 1990s, before vaccination programs against Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae , up to 5% of young children age 2 mo to 24 (up to 36) mo with fever ≥39°C (102.2°F) had occult bacteremia, most often caused by S. pneumoniae . Currently, the prevalence of occult bacteremia is <1% in febrile, well-appearing young children. The vast majority of pneumococcal occult bacteremia is transient, with a minority of these children developing new focal infections, sepsis, or other sequelae. Unimmunized and incompletely immunized young children remain at higher risk for occult bacteremia because of pneumococcus (see Chapter 209 ). Bacteremia caused by Hib or meningococcus should not be considered benign because subsequent serious invasive infection may rapidly follow the bacteremia.