I guess the spread should be measured as
Spread in a country = Cases per 1000 of population of a country (Cumulative Sum would be more appropriate on a daily basis)
and EPU as in the data is required for every country I think.
EPU = Economic Policy Uncertainty of a country on daily basis
As both are continuous variables we can do all kinds of scatter plots starting from geom_point etc. and find out if any relation exists.