asymptomatic or symptoms getting better. >> it had a lot to do with what we thought people would be able to tolerate. if we can get them to isolate, we want to make sure they're isolating in the first five days when they are maximumly infectious. >> reporter: 85 to 90% of transmission occurs in the first five days of symptom onset. still, the new guidance is drawing fierce debate among health experts. >> there is absolutely no data i'm aware about with the omicron variant that supports people coming out of isolation five days after they were first diagnosed with the virus. >> you either shut down the society, which no one wants to do or you try and get a situation where you can safely get people back particularly to critical jobs without having them be out for a full ten days. >> reporter: long testing lines are still snaking across the