COVID-19 has mainly spread through Europe in two waves: W1 between January and August 2020, and W2 which is still underway and started in September 2020.

W1 originated in China and spread throughout Europe from Cyprus and Switzerland. W2 originated mainly in the USA, Mexico, and Brazil, where the number of deaths during summer 2020 was very high, while Europe was at the end of W1.

W2 was more severe than W1 for several reasons: the season (winter); the lack of a common European strategy against the virus; no suitable information on oral hygiene and sanitation; viral drifts; controversial indications given by medical experts; the belief that chronic diseases are responsible for the deaths of elderly people; confusing information provided by media.