October 24, 2021 Analysis of EU national data

Summary: In the past few weeks, daily growth rates for cases have increased significantly in the majority of European nations, meaning that infection rates are growing rapidly. This fall resurgence has not been seen in Canada or the US.

The comparison of growth rates now and 4 weeks ago are shown in the figure below for US states, Canadian provinces, and European nations. The situation in Europe is very concerning, showing an increase in growth rates by about 5%/day or more, for most countries. US and Canadian studies are posted here.

growth_change

Fits to case data

The plots below show the case and death data for 29 EU nations. The data fits were done using data up until October 23, 2021.

The large green, grey, and indigo circles are the daily cases, hospitalizations, and deaths respectively, averaged over each week. The smaller points show the daily values. The case data are used to define the periods for which transmission rate appears to be constant. The vertical lines show where the transmission rate is changed.

If the susceptible fraction is roughly constant, constant transmission rates lead to steady exponential growth or decline during, which appear as straight lines on these log-scale plots. With immunity growing, these lines are no longer straight - bending downwards due to the herd effect. The solid curves show the model expectations for cases, hospitalizations, and deaths, as determined from the case data.

The fraction of infections that lead to hospitalization or death are calibrated only to recent data. The extent that the model projection curves match earlier hospitalization and death data indicates whether probabilities for infections leads to severe disease is changing or not.

Since this analysis started in July, fine tuning of the model for dates prior to May was not done, resulting in some discrepency with data.

The dashed curves separately show the reported cases interpretted as coming from variants of concern, divided into two types B.1.1.7 (alpha) and B.1.617.2 (delta). The very rapid growth of cases is a combination of relaxing restrictions and the introduction of the delta variant.