Passengers mask up on the Athens metro
![Passengers mask up on the Athens metro](https://www.ekathimerini.com/wp-content/uploads/2021/01/metro_web.jpg)
A woman wearing a protective face mask walks past a metro wagon during rush hour in Athens Thursday. While masks are not obligatory attire and some experts have brought their efficiency to guard against Covid-19 into question, many people prefer to err on the side of caution. [EPA]