National case definition: Varicella (Chickenpox)

Date of last revision: May 2008
Date of last review: May 2008

National notification

Only confirmed cases of disease should be notified.

Type of surveillance

Routine case-by-case notification to the federal level

Enhanced active case-by-case notification by paediatric tertiary care hospitals involved in the Immunization Monitoring Program, Active (IMPACT)

Case classification

Confirmed case

Clinical evidence of illness and laboratory confirmation of infection:

• isolation or direct antigen detection of varicella-zoster virus (VZV) from an appropriate clinical specimen
• or
• detection of VZV DNA
• or
• seroconversion or a significant rise (e.g. fourfold or greater) by any standard serologic assay in varicella-zoster IgG titre between acute and convalescent sera
• or
• positive serologic test for varicella-zoster IgM antibody
• or
• Clinical evidence of illness in a person with an epidemiologic link to a laboratory-confirmed case of chickenpox or VZV infection

Probable case

Clinical evidence of illness in the absence of laboratory confirmation or epidemiologic link to a laboratory-confirmed case

Laboratory comments

Vaccine and wild-type VZV strains can be differentiated by PCR-based protocol available at the National Microbiology Laboratory.

Clinical evidence

Clinical illness is characterized by a rash with rapid evolution of macules to papules, vesicles and crusts; all stages are simultaneously present; lesions are superficial and may appear in crops.

ICD code(s)

• ICD-10 code(s)
  • B01 Varicella
• ICD-9/ICD-9CM code(s)
  • 052 Chickenpox

Comments

Probable case definitions are provided as guidelines to assist with case finding and public health management, and are not for national notification purposes.

References

National Microbiology Laboratory Guide to Services. VZV: Strain differentiation of extracted DNA samples using real-time PCR methodology. 2008. Retrieved May 2008, from http://www.nml-lnm.gc.ca/english/guide/guideview.asp?key=15

Previous case definitions

Canadian Communicable Disease Surveillance System: disease-specific case definitions and surveillance methods. Can Dis Wkly Rep 1991;17(S3).

Case definitions for diseases under national surveillance. CCDR 2000;26(S3).