Respiratory virus trends in Canada: Understanding the data

Abbreviations, definitions and technical notes on the weekly summary of respiratory viruses detected in Canada.

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Abbreviations

A(H1N1)pdm09
Influenza A(H1N1)pdm09
A(H3)
Influenza A(H3N2)
A(UnS)
Influenza A(Unsubtyped)
ADV
Adenovirus
COVID-19
Coronavirus disease 2019
EORLA
Eastern Ontario Regional Laboratory Association
EV/RV
Enterovirus/Rhinovirus
HCoV
Human coronavirus 229E/OC43/NL63/HKU1
HMPV
Human metapneumovirus
HPIV
Human parainfluenza virus
N/A
Not available
PHOL
Public Health Ontario Laboratory
RSV
Respiratory syncytial virus
RVDSS
Respiratory Virus Detection Surveillance System
SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2
UHN
University Health Network

Data source

Data are collected through the Respiratory Virus Detection Surveillance System (RVDSS). RVDSS is a long-standing laboratory surveillance system consisting of provincial, territorial, and regional public health laboratories and some hospital laboratories. There are reporting laboratories in all provinces and territories, but not all respiratory virus testing in Canada is captured through RVDSS. Laboratories report data for up to 8 respiratory viruses:

Laboratories perform molecular testing for these viruses and report the number of tests and positive detections for each virus each week throughout the year.

Most tests are conducted on:

Outpatient cases with symptoms of respiratory virus infection may be targeted, but testing is typically limited to people at higher risk. Respiratory testing algorithms vary by province or territory.

Data use

RVDSS laboratory data are one of the main surveillance components for monitoring respiratory virus activity in Canada. Weekly percentage of tests positive (also referred to as percent positivity) is the primary indicator used to assess repiratory virus transmission trends over time and place. This indicator is calculated from submitted RVDSS data as:

Weekly percentage of tests positive (%) = Number of positive detections in a week Number of tests in a week x 100 %

Influenza laboratory data submitted through RVDSS is also summarized in weekly FluWatch reports and as well as annual and midseason influenza reports. RVDSS percent positivity data are used to determine the start and end of seasonal influenza epidemics.

RVDSS laboratory data are also used to fulfil Canada’s international respiratory virus surveillance responsibilities. Each week, we submit aggregate data to the World Health Organization's (WHO) RespiMart and to the Pan American Health Organization (PAHO) for inclusion in their weekly situation reports on respiratory viruses.

For more information, please refer to:

Technical notes

Data in this report represent surveillance data available at the time of analysis. Delays in the availability and reporting of data may cause data to change retrospectively.

RVDSS does not capture all respiratory virus testing in Canada.

Data are aggregated by RVDSS surveillance weeks. This allows the comparison of current data to historical data. Surveillance weeks begin on Sunday and end on the following Saturday.

This report only presents detailed data for the current respiratory virus season. Surveillance for each respiratory virus season starts on week 35 of a calendar year and ends on week 34 of the following calendar year. This 1-year period begins and ends around the end of August. Detailed data from previous respiratory virus seasons can be accessed through the archives section of this report.

RVDSS integrated SARS-CoV-2 surveillance at the beginning of the 2022-2023 season; no prior data are available for historical comparison.

Differences in RVDSS indicators across jurisdictions can reflect differences in testing algorithms and reporting, as well as true differences in virus activity. Use caution when comparing indicators across jurisdictions. SARS-CoV-2 testing and reporting differences were greatest when SARS-CoV-2 was first included in the RVDSS, but are expected to diminish over time.

N/A is used to identify data that is not available. Data may be unavailable if it was not reported for the current surveillance week. Alternatively data may be unavailable if a reporting laboratory does not collect/report data for specific viruses.

Respiratory virus trend assessments (increasing/decreasing/stable) are currently based on PHAC subject matter expert interpretation of week-to-week changes in respiratory virus laboratory detections and percent positivity. Set thresholds for trend assessment are under development.

Unless otherwise specified, the term influenza includes influenza A and influenza B positive detections.

Some public health laboratories in Canada perform subtyping on influenza specimens from other laboratories. When identified, these subtype detections are not included in total influenza A detection counts; in these instances, total influenza A detection counts may not equal the sum of influenza A subtype detections. Total influenza A and B positive counts are used to calculate percentage of tests positive.

Changes to testing practices during the COVID-19 pandemic caused changes to RVDSS indicators (also referred to as ‘measures of respiratory virus activity’). Counts of tests and positive detections have increased due to higher testing levels. Percentage of tests positive is likely biased downwards due to the addition of SARS-CoV-2 to testing panels. Due to these changes, seasonal data from before the COVID-19 pandemic are not presented in this report.

Provincial and Territorial Respiratory Virus Laboratory Surveillance Reports

The following links are provincial and territorial websites that provide more detailed respiratory virus surveillance data. Data differences are possible as RVDSS doesn’t capture all respiratory virus testing in Canada.

British Columbia
BCCDC Respiratory Virus Data Reports
Alberta
Respiratory Virus Dashboard
Saskatchewan
Community Respiratory Illness Surveillance Program (CRISP) Reports
Manitoba
Provincial Respiratory Surveillance Reports
Ontario
Ontario Respiratory Virus Tool
Quebec
Données COVID-19 au Québec
Surveillance de l'influenza et autres virus respiratoires
New Brunswick
Respiratory Watch
Prince Edward Island
PEI Respiratory Illness Summary
Nova Scotia
Respiratory Watch
Newfoundland and Labrador
Respiratory Activity Dashboard
Yukon
Respiratory Surveillance Report
Northwest Territories
N/A
Nunavut
N/A

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