Sweden winter time much less tourists and business travelers. Also around 50% live as single occupancy residence. At least on paper Portugal is very little travel between them and Spain and the rest of the world for that matter and east Europe wasn’t hit as hard Many countries in the west are not as comfortable or used to wearing masks in general. In general all of the following variables COULD also be confounding: The amount of cross-border traffic into and out of a country (tourism or business related) After the lockdowns the amount of travel within a country (interstate) including whether or not a country has domestic flights, heavy use of crowded public transportation systems such as subways and buses. The geographic size of the country and how densely or sparsely populated it is The underlying health of the communities. Also including certain populations appear to have more resistance genetically to Covid? The ages as some countries’ populations are significantly younger or older than other countries. Income in particular relating to living in compact quarters or housing, which can also be tied to cultural or religious beliefs. Meaning in some societies people are a lot less likely to live by themselves.