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Varicella / Chickenpox
2010 Case Definition

CSTE Position Statement(s)

  • 09-ID-68

Clinical Description

An illness with acute onset of diffuse (generalized) maculo-papulovesicular rash without other apparent cause.

Laboratory Criteria for Diagnosis

  • Isolation of varicella virus from a clinical specimen, OR
  • Varicella antigen detected by direct fluorescent antibody test, OR
  • Varicella-specific nucleic acid detected by polymerase chain reaction (PCR), OR
  • Significant rise in serum anti-varicella immunoglobulin G (IgG) antibody level by any standard serologic assay.

Case Classification

Probable

An acute illness with

  • Diffuse (generalized) maculo-papulovesicular rash, AND
  • Lack of laboratory confirmation, AND
  • Lack of epidemiologic linkage to another probable or confirmed case.

Confirmed

An acute illness with diffuse (generalized) maculo-papulovesicular rash, AND

  • Epidemiologic linkage to another probable or confirmed case, OR
  • Laboratory confirmation by any of the following:
    • Isolation of varicella virus from a clinical specimen, OR
    • Varicella antigen detected by direct fluorescent antibody test, OR
    • Varicella-specific nucleic acid detected by polymerase chain reaction (PCR), OR
    • Significant rise in serum anti-varicella immunoglobulin G (IgG) antibody level by any standard serologic assay.

Comments

Two probable cases that are epidemiologically linked would be considered confirmed, even in the absence of laboratory confirmation.

In vaccinated persons who develop varicella more than 42 days after vaccination (breakthrough disease), the disease is almost always mild with fewer than 50 skin lesions and shorter duration of illness. The rash may also be atypical in appearance (maculopapular with few or no vesicles).

Laboratory confirmation of cases of varicella is not routinely recommended; laboratory confirmation is recommended for fatal cases and in other special circumstances.



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