[1] Qi SX, Zhao X, Hao P, Liu NK, Gao GF, Song Y, et al. Two reemergent cases of COVID-19 — Hebei Province, China, January 2, 2021. China CDC Wkly 2021;3(2):25 − 7. http://dx.doi.org/10.46234/ccdcw2021.006CrossRef
[2] Chen HY, Huang XY, Zhao Z, Song Y, Hao P, Jiang H, et al. The first case of new variant COVID-19 originating in the United Kingdom detected in a returning student — Shanghai Municipality, China, December 14, 2020. China CDC Wkly 2021;3(1):1 − 3. http://dx.doi.org/10.46234/ccdcw2020.270CrossRef
[3] Chen FJ, Li BS, Hao P, Song Y, Xu WB, Liu NK, et al. A case of new variant COVID-19 first emerging in South Africa detected in airplane pilot — Guangdong Province, China, January 6, 2021. China CDC Wkly 2021;3(2):28 − 9. http://dx.doi.org/10.46234/ccdcw2021.007CrossRef
[4] Bai L, Wang YR, Wang YBN, Wu YN, Li N, Liu ZP. Controlling COVID-19 transmission due to contaminated imported frozen food and food packaging. China CDC Wkly 2021;3(2):30 − 3. http://dx.doi.org/10.46234/ccdcw2021.008CrossRef