COVID-19 

• Lab testing data: Public Health Ontario, Ontario Respiratory Virus Tool, extracted Thursdays. PHO Laboratory data: Influenza A, Influenza B and Respiratory Syncytial Virus (RSV) data used until the week of June 23, 2024. Ontario Laboratory Information System (OLIS): COVID-19 used March 2020 onward; Influenza A, Influenza B and Respiratory Syncytial Virus (RSV) used the week of June 30, 2024 onwards. 
• Outbreak data (July 2024 onwards for COVID-19, all years for other diseases): Integrated Public Health Information System (iPHIS), extracted Thursday mornings to reflect currently input data on outbreaks reported by the end of the most recent surveillance week.
• Historical COVID-19 outbreak data (March 2020-June 2024): Public Health Case and Contact Management (CCM) Solution, extracted June 27, 2024.
• Hospital bed occupancy data: Ministry of Health, SAS Visual Analytics Tool, COVID Regional Hospital and Hospital Utilization reports, extracted Thursdays, to reflect bed occupancy for the most recent surveillance week.
• Emergency department visits data: Acute Care Enhanced Surveillance (ACES) application, extracted Thursdays, to reflect visits that occurred during the most recent surveillance week.

• The dashboard is updated weekly, on Thursdays. Numbers will update dynamically within the dashboard by approximately 4 pm on Thursdays, as server times allow.
• Data throughout the dashboard is organized into respiratory seasons, using surveillance weeks.
  • Each respiratory season runs from approximately September 1 of one year to August 31 of the following year.
  • Surveillance weeks run from Sunday to Saturday.
  • The surveillance week typically containing September 1 (week 35) is used as the first week of each respiratory season.
  • The current respiratory season (2024-25) began on August 25, 2024, and will end on August 30, 2025.
  • All dates are based on the FluWatch Public Health Agency of Canada surveillance week schedule.
• Numbers in the dashboard should not be expected to match numbers reported by other sources, due to different data extraction times and methodological differences.
• All data in the dashboard are dynamic and subject to change with future refreshes of the dashboard.
  • iPHIS is a dynamic disease reporting system that allows ongoing updates to data previously entered.
  • As a result, data extracted from iPHIS represent a snapshot at the time of extraction and may differ from previous or subsequent reports.
  • Numbers may increase or decrease to reflect our most up to date information. Numbers may change significantly when data cleaning initiatives are completed.
• All data except the data shown in the “Hospital Bed Occupancy” tab includes only individuals whose main usual residence is in Halton Region.

The Snapshot tab provides a summary of current respiratory virus activity among Halton residents. It includes three indicators (percent positivity, reported outbreaks, and hospital bed occupancy), shown separately for COVID-19 and influenza. Note that percent positivity for influenza includes both influenza A and influenza B.

Activity in the current surveillance week is compared to activity in the previous surveillance week, and this comparison is represented as a “Weekly change”. The indicator’s activity level may be considered higher than the previous week (a dark blue upward arrow); similar to the previous week (a grey left-right arrow); or lower than the previous week (a light blue downward arrow). The criteria used to determine the weekly change is shown in the table below.

• Percent positivity is calculated as the total number of positive tests over a 7-day surveillance week, divided by the total numbers of tests conducted during the surveillance week.
• Tests are assigned to a surveillance week based on the specimen collection date.
• The unit of analysis is the number of tests completed. Individuals may have more than one test conducted during the same week or over time, and each test will be counted.
• Trends over time should be interpreted with caution as testing methods and testing eligibility have changed over time.
• Percent positivity may be unstable and should be interpreted with caution when there are low numbers of tests conducted.
• Lab data are assigned to a health unit using patient postal code. When patient postal code is missing, submitter postal code is used to assign the public health unit. This could lead to test results being assigned to a different health unit from where an individual resides.

• Outbreaks are assigned to a surveillance week based on the date the outbreak was reported to Public Health.
• The criteria for declaring an outbreak can change over time. The dashboard reflects outbreaks as they were entered into iPHIS or CCM according to the outbreak criteria in place at the time.
• Only outbreaks in institutional and congregate settings are shown on the dashboard. Outbreaks in other settings have not been included.
• Institutions include hospitals, long-term care homes, and retirement homes.
• Congregate living settings refer to a range of facilities where people (most or all of whom are not related) live or stay overnight and use shared spaces (e.g. common sleeping areas, bathrooms, kitchens). Examples include shelters and group homes.
• The “Other” category includes outbreaks of entero/rhinovirus, parainfluenza, metapneumovirus, measles, and unspecified respiratory infection. These outbreaks do not involve COVID-19, influenza, or RSV.
• An outbreak can involve more than one respiratory disease, known as a multi-organism outbreak. The dashboard does not include a count of diseases involved in outbreaks. In the dashboard, a multi-organism outbreak is counted as only one outbreak, unless it involves more than one of COVID-19, influenza, or RSV. For example, an outbreak involving both COVID-19 and metapneumovirus would be reported as a single COVID-19 outbreak. An outbreak involving COVID-19, metapneumovirus, and influenza would be reported as two outbreaks – a COVID-19 outbreak and an influenza outbreak. An outbreak involving metapneumovirus and parainfluenza only would be reported as a single “Other” outbreak.
• Active outbreaks include any outbreaks that were ongoing (not yet declared over) for at least one day during the most recent surveillance week, regardless of when they were first reported.
• Reported outbreaks (shown both in the graph and above the graph) are only counted once during the week they are reported and are not counted again, even if the outbreak remains ongoing/active.
• It takes time for outbreaks to be declared over and for their records to be updated in iPHIS. The active outbreak count can be affected by delays in updating iPHIS records as outbreaks are declared over and all related documentation is completed and updated.

• Bed occupancy data became available in March 2020 for COVID-19, but only in November 2022 for influenza and RSV.
• Data shown represent the average number of patients occupying a bed in a Halton hospital who have COVID, influenza, or RSV during a given surveillance week. In other words, occupancy is calculated by averaging the occupied beds across the 7-day surveillance week, since the number of occupied beds can vary each day.
• The beds in Halton hospitals may be occupied by a resident from anywhere. Any Halton residents hospitalized outside Halton are not shown.
• The individual may be hospitalized due to complications of COVID-19, influenza, or RSV, or they may be hospitalized for other reasons but also were found to be infected with COVID-19, influenza, or RSV.
• An individual may be infected with more than one of COVID-19, influenza, or RSV, in which case the occupied bed will be counted separately in each category.

• Visits are assigned to a surveillance week based on the date the individual presented to the emergency department.
• Includes visits made by Halton residents to the emergency department of any hospital in Ontario.
• Visits are assigned automatically to a category based on presenting symptoms (“chief complaint”). As this is a syndromic surveillance source, visits for a variety of conditions with symptoms similar to a respiratory infection may be classified as respiratory or influenza-like illness, but may not actually represent a confirmed respiratory virus infection.
• The percentage of visits for respiratory or influenza-like illness is calculated by dividing the number of visits during the surveillance week that were classified into these categories by the total number of emergency department visits within the surveillance week.

• Variability between respiratory seasons exists for many reasons, including: the strains of viruses in circulation; how well available vaccines match the circulating strains; which age groups are most affected; and the severity of illness resulting from infection.
• Changes to laboratory testing eligibility over time also alters the number of people and the proportion of collected samples that are tested for respiratory viruses like influenza, COVID-19, and RSV.
• Viral containment measures can also impact viral activity. For example, while they were in place, COVID-19 restrictions incidentally reduced activity for other respiratory viruses like influenza and RSV.
• Therefore, comparing disease activity across seasons should be done only with extreme caution, as comparability is limited by changes over time in viral activity, testing eligibility, case and outbreak definitions, and viral containment measures.

• Wastewater data is not shown on the dashboard because viral testing at wastewater treatment plants in Halton has been discontinued, as in most other jurisdictions within Ontario. Previously, this testing was conducted under the provincial Wastewater Surveillance Initiative (WSI), which officially ended on July 31, 2024.
• Data from wastewater testing at the remaining sites in Ontario (all located outside Halton) can be found in the Public Health Agency of Canada’s Wastewater monitoring dashboard (external link).