National case definition: Rubella

Date of last revision/review: May 2008

National reporting

Only confirmed cases of disease should be notified.

Type of surveillance

Active, weekly case-by-case notification (including zero-notification) by provincial and territorial ministries of health to the Canadian Measles/Rubella Surveillance System (CMRSS)

Case classification

Confirmed case

Laboratory confirmation of infection in the absence of recent immunization (see Clinical evidence section) with rubella‑containing vaccine:

• isolation of rubella virus from an appropriate clinical specimen
  or
• detection of rubella virus RNA
  or
• seroconversion or a significant (e.g. fourfold or greater) rise in rubella IgG titre by any standard serologic assay between acute and convalescent sera
  or
• positive serologic test for rubella IgM antibody using a recommended assay (see Laboratory comments section) in a person with an epidemiologic link to a laboratory-confirmed case or who has recently travelled to an area of known rubella activity
  or
• Clinical illness (see Clinical evidence section)in a person with an epidemiologic link to a laboratory-confirmed case

Probable case

Clinical illness

• in the absence of appropriate laboratory tests
  or
• in the absence of an epidemiologic link to a laboratory-confirmed case
  or
• in a person who has recently travelled to an area of known rubella activity

Laboratory comments

• IgM serology has the potential for false-positive findings. If the clinical presentation is inconsistent with a diagnosis of rubella or in the absence of recent travel/exposure history, IgM results must be confirmed by the other listed confirmatory methods. Rubella avidity serology is recommended for IgM positive results in pregnant women.
• Most acute rubella cases develop IgM after 5 days post rash onset. Therefore, a suspected rubella case in which serum collected < 5 days after rash onset initially tests IgM negative should have a second serum collected > 5 days after onset for retesting for IgM.
• Further strain characterization is indicated for epidemiologic, public health and control purposes.

Clinical evidence

Clinical illness is characterized by fever and rash, and at least one of the following:

• arthralgia/arthritis
• lymphadenopathy
• conjunctivitis

The most frequent reaction to measles-mumps-rubella (MMR) immunization is malaise and fever (with or without rash) occurring 7-12 days after immunization. However, this should be determined for each case, as these reactions and time frames can vary (Canadian Immunization Guide, 7^th edition).

ICD code(s)

ICD-10 code(s)

• B06 Rubella

ICD-9/ICD-9CM code(s)

• 056 Rubella

Type of international reporting

Weekly reporting to the Pan American Health Organization, in accordance with the goal of eliminating rubella and congenital rubella syndrome in the Western Hemisphere.

Comments

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

Active weekly surveillance began in 2006. All cases are reviewed by the Immunization and Respiratory Infections Division (Public Health Agency of Canada) for classification before being added to the national database.

References

• Pan American Health Organization. Measles Elimination Field Guide. 2^nd edition. Scientific and Technical Publication No. 605. Retrieved May 2008, from www.paho.org/english/ad/fch/im/fieldguide_measles.pdf
• Pan American Health Organization. Elimination of Rubella and Congenital Rubella Syndrome Field Guide. Scientific and Technical Publication No. 606.

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).