pediatric emergency room physician at columbia university medical center, as well as a member of columbia's medical faculty. ladies, thanks so much for being with us. my goodness, if bwe could just get this past this thing. it's just wishful thinking i suppose. i want to ask you though dr. wen about the cdc updating guidelines today. as he i mentioned, they shortened the recommended times people should isolate when they have tested positive for covid-19 from ten days to five days if they don't have symptoms, if they wear a mask around others, for at least five more days. what do you think of that decision? as shimon was just saying at la guardia airport, might help flight crews who are kind of grounded right now. >> jim, this was a necessary step because we are facing the collapse of our critical infrastructure. the number of cases that we are seeing now -- it's really high. but it's going to get so much worse because we have exponential spread of an extremely contagious variant. the numbers now, by the way, are a significant undercount because