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. 2021 Jun 23;31(14):R918–R929. doi: 10.1016/j.cub.2021.06.049

Figure 4.

Figure 4

The spike in case numbers in the spring of 2021 was predicted by models of VOC dynamics.

Case numbers in Canadian provinces (black circles; data up to 8 March, 2021) were fit using a dynamic modeling approach, either ignoring VOC (purple) or allowing the spread of VOC with a transmission advantage of 50% (grey). In each panel, the VOC is introduced a week before the date of the first publicly reported case in each province (vertical dashed line) with initial numbers set to match the observed VOC numbers in early March. Subsequent case numbers, which were not used in the model fits, are shown as hollow circles. The spike in cases led to various emergency restrictions (vertical solid lines), which subsequently brought cases down over the next couple of weeks. Poor model predictions in a couple of provinces are likely due to migration among provinces and/or a low sampling rate for VOC (for example, genomics now indicates that B.1.1.7 was in Manitoba at least 19 days earlier than the first reported case). (Based on model fits using the Public Health Agency of Canada/McMaster model76.)