Viruses cause most pediatric infections. Mixed viral or viral-bacterial infections of the respiratory and intestinal tracts are common, as is prolonged asymptomatic shedding of some viruses in childhood, especially in young children. Thus, the detection of a virus is not always proof that it is the cause of a given illness. Viruses are often a predisposing factor for bacterial respiratory infections (eg, otitis, sinusitis, and pneumonia).
Many respiratory viruses and herpesviruses can now be detected within 24–48 hours by combining culture and monoclonal antibody techniques (“rapid culture technique”) or through antigen or nucleic acid detection techniques. Polymerase chain reaction (PCR) amplification of viral genes has led to recognition of previously undetected infections. New diagnostic tests have changed some basic concepts about viral diseases and made diagnosis of viral infections both more certain and more complex. Only laboratories with excellent quality-control procedures should be used. The availability of specific antiviral agents increases the value of early diagnosis for some serious viral infections. Table 40–1 lists diagnostic tests. The viral diagnostic laboratory should be contacted for details regarding specimen collection, handling, and shipping. Table 40–2 lists common causes of red rashes in children that should be considered in the differential diagnosis of certain viral illnesses.
Table 40–1.Diagnostic tests for viral infections. |Favorite Table|Download (.pdf) Table 40–1.Diagnostic tests for viral infections.
|Agent ||Rapid Antigen Detection (Specimen) ||Tissue Culture Mean Days to Positive (Range) ||Serology ||PCR ||Comments |
|Acute ||Paired |
|Adenovirus ||+ (respiratory and enteric) ||10 (1–21) ||– ||+ ||+ ||“Enteric” strains detected by culture on special cell line, antigen detection, or PCR |
|Arboviruses ||– ||– ||+ ||+ ||+ ||Acute serum may diagnose many forms |
|Astrovirus ||– ||– ||– ||– ||+ ||Diagnosis by electron microscopy |
|Calicivirus ||– RL ||– ||– ||– ||+ ||Diagnosis by electron microscopy; PCR generally available for norovirus; present in RL for others |
|Colorado tick virus ||On RBC ||– ||– ||RL, CDC ||+ || |
|Coronavirus ||– ||RL ||– ||+ ||+ || |
|Cytomegalovirus ||+ (tissue biopsy, urine, blood, respiratory secretions) ||2 (2–28) ||+ ||+ ||+ ||Diagnosis by presence of IgM antibody; rapid culture method generally available; low avidity antibody indicates recent infection |
|Dengue ||+ ||5 d (RL) ||+ ||+ ||+ ||Testing at CDC; 80% seropositive at 6 days |
|Enterovirus ||– ||3 (2–8) Coxsackie A difficult to culture ||– ||++ ||+ || |
|Epstein-Barr virus ||– ||– ||+ ||++ ||++ ||Single serologic panel defines infection status; heterophil antibodies less sensitive |
|Hantavirus ||– ||– ||+ ||ND ||RL ||Diagnosis by presence of IgM antibody |
|Hepatitis A virus ||– ||– ||+ ||ND ||RL ||Diagnosis by presence of IgM antibody |
|Hepatitis B virus ||+ (blood) ||– ||+ ||ND ||+ ||Diagnosis by presence of surface antigen or anticore IgM antibody |
|Hepatitis C virus ||– ||– ||+ ||ND ||+ ||Positive serology suggests that hepatitis C could be the causative agent; PCR is confirmatory. PCR may be positive before serology |
|Herpes simplex virus ||+ (mucosa, tissue biopsy, respiratory secretions, skin)...|