A staff member checks tickets at the Brussels-Midi station in Brussels, Belgium, June 15, 2020. Belgium on Monday reopened its borders to and from the United Kingdom, European Union (EU) member countries and four other countries of the Schengen zone (Iceland, Norway, Switzerland and Liechtenstein). (Xinhua/Zhang Cheng)

A staff member guides a passenger buying tickets at the Brussels-Midi station in Brussels, Belgium, June 15, 2020. Belgium on Monday reopened its borders to and from the United Kingdom, European Union (EU) member countries and four other countries of the Schengen zone (Iceland, Norway, Switzerland and Liechtenstein). (Xinhua/Zhang Cheng)

A passenger buys tickets at the Brussels-Midi station in Brussels, Belgium, June 15, 2020. Belgium on Monday reopened its borders to and from the United Kingdom, European Union (EU) member countries and four other countries of the Schengen zone (Iceland, Norway, Switzerland and Liechtenstein). (Xinhua/Zhang Cheng)

Passengers walk past a sign reminding people to wear face masks and keep distance at the Brussels-Midi station in Brussels, Belgium, June 15, 2020. Belgium on Monday reopened its borders to and from the United Kingdom, European Union (EU) member countries and four other countries of the Schengen zone (Iceland, Norway, Switzerland and Liechtenstein). (Xinhua/Zhang Cheng)

Passengers walk past the ticket office at the Brussels-Midi station in Brussels, Belgium, June 15, 2020. Belgium on Monday reopened its borders to and from the United Kingdom, European Union (EU) member countries and four other countries of the Schengen zone (Iceland, Norway, Switzerland and Liechtenstein). (Xinhua/Zhang Cheng)