Individual level Country/region level
A
Contact with a SARS-CoV-2 infected individual
++++
Case zero identified ++++ e.g. Lombardy
A Intensity of social contacts ++ +++
A Intensity of occupational contacts +++ ++
A
Confinement (level)
+++
+++ e.g. US versus EU Sweden vs Nordic countries
A
Confinement (early measures)
+++
+++ e.g. UK versus EU
A
Climatic conditions (temperature, humidity)
?
++ Hot and humid temperature may reduce infection but epidemic bursts in Brazil, Peru and Ecuador
A GDP of a country/region ? +
A Vitamin D ? +
B
Diet
?
+ The map of COVID-19 deaths in Europe and the low prevalence in Asia and Africa suggest a role for diet
B
Food
++?
+ Bibliographic analysis suggests a role for some fermented foods. Raw cabbage can be fermented in the intestine. Kefir is largely used in many low-prevalence countries.
B
Long food chain supply
++?
+ In Italy and Spain, there may be an association with long chain supply. This may be relevant since food quality differs.
B
Traditional fermented food (example of food)
++?
++ This may be a relevant issue. In former Eastern European countries, in the Balkans, in Africa and in many Asian countries with low-COVID-19 prevalence, traditional fermented foods are common (in line with short food chain supply)
B Air pollution +? +?
B Underserved area ++ ++
C Age +++
C Comorbidities (severity of COVID-19) +++ ++
C Sex ++
C Institutionalized person ++