Nine questions about Beijing's latest COVID-19 outbreak

 People line up for nucleic acid testing on June 15, 2020 at Guang'an Gymnasium in Xicheng District, Beijing. Beijing is organizing nucleic acid tests for 90,000 residents to curb a new cluster of local COVID-19 infections. [Photo by Zou Hong/chinadaily.com.cn]

Beijing has reported 106 confirmed cases of COVID-19 as of Monday at midnight since the city reported the first case in the latest outbreak on last Thursday. Why did the outbreak happen in Beijing and what has the city has done after the outbreak began?

Question 1: Who is patient zero?

After 56 days, Beijing reported a new locally transmitted case - a 52-year-old man surnamed Tang in Xicheng district on Thursday.

Tang visited a local hospital on Wednesday for recurring fever and said he had not traveled outside Beijing in the past two weeks.

On Friday, six more confirmed cases were reported. Among them, two in Fengtai district were coworkers at a meat products research institute, and one surnamed Liu said he had traveled to Qingdao in East China's Shandong province in the past two weeks.

Epidemiological investigation found both Liu and Tang had been to Xinfadi, a major farm products wholesale market in Fengtai district. Tang went there on June 3 and Liu went there on June 5.

The Qingdao health commission said disease control experts in Qingdao had ruled out the possibility that Liu, who was on a business trip to Qingdao from May 29 to June 2, picked up the infection there.

Wu Zunyou, the chief epidemiologist at the Chinese Center for Disease Control and Prevention, said on Monday that Tang started having symptoms on June 6, and another patient reported on Saturday starting symptoms on June 5.

It was still unknown if other people had symptoms earlier than this, Wu said.