ARCHIVED - Guidelines for the Prevention and Control of Mumps Outbreaks in Canada

 

4.0 Definitions

4.1 National Case Definition

Mumps is a reportable disease in all provinces and territories and notifiable at the national level. A revision of the national case definition for mumps is to be published in Spring 2009. The current national notifiable disease case definitions can be found at http://www.phac-aspc.gc.ca.

4.2 Outbreak Definition

An outbreak can be defined in many ways. When an increased number of cases are reported for a particular disease, it is important to determine that it is a true outbreak by considering factors such as historical disease activity, seasonal events, and changes in surveillance, reporting, and/or diagnostic procedures. Furthermore, what is considered an outbreak may vary across jurisdictions. Table 3 provides a working definition of mumps outbreaks.

 

Table 3. Recommendation for outbreak definition
Outbreak Confirmed cases in excess of what is expected in the jurisdiction over a given period of time.

 

Household links would generally not be considered to be an outbreak, but that determination is up to the discretion of the jurisdiction.

4.3 Case and Contact Definitions

During increased mumps activity or outbreaks, the definitions in Table 4 of a confirmed case, clinical/probable case, and contact should be used. Section 5.0 and Appendix 4 have details on preferred clinical specimens and interpretation of laboratory results. Final case classification should be based on all available information.

Table 4. Recommended definitions of cases and contacts during increased mumps activity or outbreaks
Confirmed case

Any one of the following in the absence of recent immunization (i.e., in the previous 28 days):

  1. mumps virus detection or isolation from an appropriate specimen (buccal swab is preferred);
  2. positive serologic test for mumps IgM antibody in a person who has mumpscompatible clinical illness (see Clinical Case below);
  3. significant rise (four-fold or greater) or seroconversion in mumps IgG titre;
  4. mumps-compatible clinical illness (see “Clinical/probable case” below) in a person with an epidemiologic link to a laboratory-confirmed case.
Clinical/probable case Acute onset of unilateral or bilateral parotitis lasting longer than 2 days without other apparent cause
Contact

Any of the following during the infectious period (i.e., approximately 7 days before to 5 days after symptom onset):

  1. household contacts of a case;
  2. persons who share sleeping arrangements with the case, including shared rooms (e.g., dormitories);
  3. direct contact with the oral/nasal secretions of a case (e.g., face-to-face contact, sharing cigarettes/drinking glasses/food/cosmetics like lip gloss, kissing on the mouth);
  4. children and staff in child care and school facilities (as deemed necessary by the epidemiology of the outbreak).

Refer to Section 6.3.3 if the contact is a health care worker.

4.4 Surveillance and Reporting

In Canada, the reporting of notifiable diseases is mandated by provincial/territorial legislation and regulation. The list of reportable diseases varies slightly by province and territory. Reporting by the provinces and territories to the federal level is voluntary. The Notifiable Diseases Reporting System (NDRS) is the national, passive surveillance system used to monitor more than 40 nationally notifiable infectious diseases. Since data submission to the NDRS is voluntary, there may be inconsistencies in disease case counts, variability in the frequency of data submission, and incomplete coverage (i.e. number of provinces/territories submitting). Probable cases of mumps are not nationally notifiable. Each province or territory has procedures in place for the rapid notification of cases to medical officers of health and timely reporting to the appropriate provincial or territorial public health authorities.

Most jurisdictions rely on passive surveillance for the identification of cases. When an increase in the incidence of mumps is suspected in a particular area, enhanced surveillance of cases by collection of more detailed epidemiologic, clinical, and laboratory information is encouraged; active surveillance and rapid entry into an electronic reporting system might also be considered. Detailed epidemiologic information helps identify susceptible groups and determine associations that will permit targeted interventions. The types of information to collect include demographic and clinical information (including hospitalization and complications), immunization history, laboratory results, exposure (e.g., household, school/educational institution, occupational, mass gatherings) and recent travel. Other information relevant to the outbreak may be social or cultural settings. A sample case report and follow-up form (based on those used in previous outbreaks) are included in Appendix 3.

During outbreaks, clinical specimens can be forwarded by the provincial laboratory to the National Microbiology Laboratory (NML) at PHAC for molecular characterization and strain identification, which can distinguish between vaccine and wild types of the mumps virus. Strain identification can also be used to link cases or outbreaks and to track importations.

When multiple jurisdictions are involved, it is not always clear who should report a case. Case reporting is important for describing and monitoring the epidemiology, impact, and spread of an outbreak. Therefore, during outbreaks, the jurisdiction that initially identifies and primarily handles the case is asked to report it. This decision rule is flexible and should be evaluated for each case, considering place of residence, travel itinerary, and the public health response or intervention that was implemented.

Mumps cases that are confirmed as per the outbreak case definition (Table 4) should remain part of routine provincial/territorial and national reporting of mumps. However, it is important to note that, while outbreak definitions may differ from routine surveillance definitions, they will have increased sensitivity because of increased disease activity.


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