The Chinese city of Tianjin, known as a major gateway to Beijing, has begun citywide COVID-19 nucleic acid testing, state-run media reported Monday, just weeks before the Winter Olympics in the capital.The stepped-up anti-epidemic measure was prompted by the confirmation Saturday of two community infections with the highly contagious Omicron variant in the city of 1.4 million people.If residents do not get tested within a specified time, their "health code" on a smartphone will turn to orange from green, the media said, meaning they would be prohibited from boarding trains and buses as well…READ FULL ARTICLE