Medical workers collect throat swabs from construction workers at a construction site in Dongcheng District of Beijing, capital of China, June 17, 2020. From June 15 to 17, a total of 1,042 workers of China Construction Third Engineering Bureau Co., Ltd (Beijing) received nucleic acid tests for COVID-19. (Photo by Ke Yuqian/Xinhua)

Medical workers collect throat swabs from construction workers at a construction site in Dongcheng District of Beijing, capital of China, June 17, 2020. From June 15 to 17, a total of 1,042 workers of China Construction Third Engineering Bureau Co., Ltd (Beijing) received nucleic acid tests for COVID-19. (Photo by Ke Yuqian/Xinhua)

Medical workers collect throat swabs from construction workers at a construction site in Dongcheng District of Beijing, capital of China, June 17, 2020. From June 15 to 17, a total of 1,042 workers of China Construction Third Engineering Bureau Co., Ltd (Beijing) received nucleic acid tests for COVID-19. (Photo by Ke Yuqian/Xinhua)