新冠病毒时间线：病毒是何时、如何传播给人类的？

随着科学家继续对世界各地的样本展开研究，有证据表明，新冠病毒早在2019年3月就已经出现，这远远早于同年12月在武汉发现的时间点。CGTN在视频中将动画与专家采访相结合，梳理出新冠病毒时间线。

The current timeline for the COVID-19 pandemic begins with a cluster of viral pneumonia cases that found in Wuhan in late December 2019，and were reported to the World Health Organization on December 31，2019。 However，as scientists continue to check samples going back through the year，there has been evidence to suggest the virus was moving around as early as March 2019。In Barcelona，wastewater samples have been tested for the SARS-CoV-2 virus. What is the origin of the virus？How and when did it spillover to humans？