spring semester, delaying reopening, or moving to virtual learning due, of course, to concerns over the omicron variant. now, that is in the united states. let's look internationally. china is imposing a major covid lockdown on a fourth city, and this one appears to be the biggest yet. in xian, some 30 million people are being forced to stay home. like in wuhan last year if you remember, transportation to and from the city has been suspended. mass testing, as you can see, is already underway. schools in many public facilities have been shutdown with only essential services like super markets and hospitals staying open. selena wang is tracking the story for us from tokyo. selena, this is a huge undertaking, but the major -- the first time a major city has been placed under lockdown in china. what does this mean in theory for those who will be under lockdown? >> reporter: yeah, isa, for