There's mounting evidence that people are no longer infectious from day 8 after symptoms first appear onward. A German study tracked only a handful of patients, but tracked them very rigorously, with multiple swabs each day for 30 days and were unable to cultivate a live viral isolate after day 8 in ALL cases, even when the patient's viral load was still extremely high. (But in fairness, a bunch of viruses work this way, where patients are still sick and their viral load is high, but they cease being contagious after a few days. Eight days is still a long time, but you shouldn't have to quarantine for a month, we hope.)