Daily numbers give a sense of whether the number of new infections is growing and how quickly. When experts talk about using physical distancing to “flatten the curve” and keep the strain on the health-care system manageable, this is the curve they’re talking about.
However, there are a few days between each of the following: infection, the onset of symptoms, testing, and test results, meaning that the numbers typically reflect new infections a couple of weeks earlier.
A sudden jump in numbers may reflect a change in how data is being reported. For example, in Ontario there was a spike in cases on Oct. 13, resulting from the inclusion of cases that hadn’t been reported on Oct. 12. In B.C., data is not available over the weekend, resulting in a spike on Mondays when cases from the weekend are reported. Jumps can also occur when changes are made to who’s allowed to be tested and how many people are tested.