Spread of COVID-19 across Public Health Units in Southern Ontario (Feb 22 – Apr 6, 2020)

On March 30, 2020, the Ontario government enhanced its daily reporting of COVID-19 cases in the province. We summarized how these enhancements – especially the daily epidemiological summary – might address our critique of the government’s earlier reporting.

Shortly after introducing its daily epidemiological summary, the Ontario government also began publishing case data of confirmed positive COVID-19 cases as initially reported by public health units across the province. The Ontario government identified the sources and some limitations of its dataset.

Data Sources (Case Data)

  • The data for this report were based on information extracted from the Ontario Ministry of Health (MOH) integrated Public Health Information System (iPHIS) database at 4 p.m.
  • iPHIS is a dynamic disease reporting system, which 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.

iPHIS data caveats:

  • The data only represent cases reported to public health and recorded in iPHIS. As a result, all counts will be subject to varying degrees of underreporting due to a variety of factors, such as disease awareness and medical care seeking behaviours, which may depend on severity of illness, clinical practice, changes in laboratory testing, and reporting behaviours.
  • Only cases meeting the confirmed case classification as listed in the MOH COVID-19 case definition are included in the report counts.
  • Case episode date is based on an estimate of the best date of disease onset. This date is calculated based on either the date of symptom onset, specimen collection/test date, or the date reported to public health.
  • Orientation of case counts by geography is based on the diagnosing health unit.

With these (well-deserved) caveats in mind, the Ontario government’s dataset allows us to map the spread of COVID-19 across the province over time.

As a start, we have generated an interactive map of the growing number of confirmed cases of COVID-19 by public health unit in southern Ontario over a 45 day period (February 22 – April 6, 2020).

NOTE: The map represents data included in the dataset published on April 7, 2020.