Covid-19 has dampened the travel plans of millions of Chinese for the Lunar New Year for a third straight year. Pre-pandemic, the celebration would see as many as 3 billion trips made across China, and was the world's largest annual migration of people. But resurgent virus outbreaks have forced many to cancel their plans. Chinese officials - still pursuing a zero-Covid strategy - have enforced strict measures with days to go before the 2022 Winter Olympics begin.