As new infections decline overall in China, recent rebounds are drawing concern. Some districts in the northeastern city of Harbin and the southern city of Guangzhou have been rated medium risk. Beijing's Chaoyang district is now a high-risk area. Local authorities cite a recent cluster caused by an imported case. A student returned from the U.S. in mid-March. He reported cough and nasal symptoms but tested negative twice. During a two-week quarantine, he showed no further symptoms and still tested negative. Several days after his discharge, he had a fever and other symptoms and tested positive. His mother and brother also developed symptoms but didn't go to the hospital. Three of the five other people in his home have tested positive. Sixty-two other people are now under observation due to close contact. We see what looks like cluster infections in the recent coronavirus bump, including in Beijing and Heilongjiang province. What does that tell us? Do we have to worry about the recent cluster infections? Professor Zhao Dahai, an executive director of Shanghai Jiao Tong University and Yale University Joint Center for Health Policy, gives his viewpoints on CGTN.