Experts from the World Health Organization and China have recommended four possible ways the coronavirus first originated. They say animal-to-human transmission is the most likely scenario. On the opposite end of the spectrum, they say the lab leak theory is "extremely unlikely." Their estimates are based on field work carried out in central China's Wuhan earlier this year. Next, they're calling for investigations to be carried out in other parts of the world. CGTN reporter Zhou Jiaxin has more.