When China was suppressing the news about the coronavirus when a doctor sounded the alarm in December,and virus started to spread, why did the virus not spread to other large population centers of China like Shanghai and Beijing before Wuhan was locked down. It was apparently able to spread to Japan, Korea, US and Italy quite easily. But not Shanghai, Beijing, Guangjhou or Hongzhou! Can somebody enlighten me as to what happened here? How did Virus know to stay out of all these population centers?"