9 Things Experts Have Learned About Covid-19 So Far

The disease has not changed, but scientific understanding has evolved dramatically

In a chemistry lab, a male researcher holds a tube with the coronavirus virus.

The first documented case of Covid-19 in the United States was reported half a year ago, days before early warnings from the U.S. Centers for Disease Control and Prevention (CDC) that a “very serious public health threat” loomed. Yet health…