Varicella (Chickenpox)
1999 Case Definition
Clinical case definition
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
- Direct fluorescent antibody (DFA), or
- Polymerase chain reaction (PCR), or
- Significant rise in serum varicella immunoglobulin
G (IgG) antibody level by any standard serologic assay
Case classification
Probable: a case
that meets the clinical case definition, is not laboratory confirmed,
and is not epidemiologically linked to another probable or confirmed
case
Confirmed: a case that is laboratory confirmed
or that meets the clinical case definition and is epidemiologically
linked to a confirmed or probable case
Notes
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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