Four reasons experts say coronavirus cases are dropping in the United States

The rate of newly recorded infections is plummeting from coast to coast and the worst surge yet is finally relenting. But scientists are split on why, exactly, it is happening. Some point to the quickening pace of coronavirus vaccine administration, some say it’s because of the natural seasonal ebb of respiratory viruses and others chalk it up to social distancing measures. And every explanation is appended with two significant caveats: The country is still in a bad place, continuing to notch more than 90,000 new cases every day, and recent progress could still be imperiled, either by new fast-spreading virus variants or by relaxed social distancing measures.