Timeline represents the day COVID-19 cases were confirmed by testing, not the onset of illness. Cases confirmed today include people who became ill sometime in the past.
Data excludes "probable" cases that have not been confirmed by testing. However, because of the limitations of available data, a small number of probable cases may be included between April 5-20. As a result, the number of confirmed cases for April 21 is an estimate and lower than the actual number of confirmed cases that day.
The seven-day average is used to smooth out the data over time and avoid large swings from a single day's number. It is calculated by averaging the cases from the current day and six previous days.