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Varicella (Chickenpox)
2010 Case Definition
CSTE Position Statement Number : 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) maculopapulovesicular rash, AND
- Lack of laboratory confirmation, AND
- Lack of epidemiologic linkage to another probable or confirmed case.
Confirmed:
- An acute illness with diffuse (generalized) maculopapulovesicular 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.
Comment
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.
See also:
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