Today’s episode: Learning as we go. The thing that makes COVID-19 so tricky is its newness. It’s a disease that literally did not exist in humans until a few months ago. There was no handbook for treating it, no established way to screen for it and, as has become painfully clear, no detailed protocols for how doctors should handle the waves of sick patients. That has meant that health workers at virtually every point on the spectrum — from paramedics to primary-care doctors to ICU specialists —