Unique questions that help identify whether an infectionis causing the patient’s symptoms include a detailed environmental history (including sick contacts, travel, and animal exposure) (see Table 93-1). Certain infections are more common in specific geographic areas. For instance parasitic infections are more common in tropical climates. Diarrhea maybe bacterial, viral, or parasitic in the tropics, but in temperateclimates parasitic causes of diarrhea, other than giardiasis,are much less likely. Certain fungal infections have specificgeographic distribution (coccidioidomycosis in the southwestern United States, blastomycosis in the upper Midwest,and histoplasmosis in central United States). In other areas,fungal pneumonias are rare except in immunocompromised persons.
An immunization history is critical for determining susceptibility to vaccine preventable diseases. Family history, especially of unexpected deaths of male infants, may suggest familial immunodeficiency (see Chapters 73 through 76). Localization of symptoms to a specific site may narrow diagnostic possibilities (see Table 93-2).
A complete physical examination is essential to identify signs of infection, which may be systemic, such as fever and shock, or focal, including swelling, erythema, tenderness, and limitation of function. Many infectious diseases are associated with characteristic cutaneous signs (see Table 97-1). Accurate otolaryngologic examination is critical for diagnosing upper respiratory tract infections and otitis media, the most common childhood infectious diseases in the United States.
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Fever and Rash Fever without a Source Fever of Unknown Origin
Fever does not always represent infection. Rheumatologic disease, inflammatory bowel disease, Kawasaki disease, poisoning, and malignancy also may present with fever. Particularly, children with overwhelming infection may be afebrile or hypothermic. Common symptoms, such as bone pain or lymphadenopathy that suggest infection, may also be due to leukemia, lymphoma, juvenile idiopathic arthritis, or Kawasaki disease (see Chapters 88, 89, and 153). Acute mental status changes or focal neurologic impairment could be manifestations of infections (encephalitis, meningitis, or brain abscess) or noninfectious causes (brain or spinal tumors, inflammatory conditions, postinfectious sequelae, or impairment from toxic ingestions or inhalants). Many manifestations of mucosal allergy (rhinitis, diarrhea) may mimic common infectious diseases (see Chapter 77).
Some infections are prone to recurrence, especially if treatment is suboptimal (inadequate antimicrobial or shorter duration). Recurrent, severe, or unusual (opportunistic) infections suggest the possibility of immunodeficiency (see Chapters 72 and 125).
Laboratory diagnosis of infection includes examination of bacterial morphology using Gram stain, various culture techniques,