It’s the last news anyone wants to hear: one year after the United States was slammed with its first wave of COVID-19—which was followed by even worse second and third waves—public health experts are worried that the country is headed for a fourth major spike. During a White House coronavirus briefing on Monday, Rochelle Walensky, the new director of the U.S. Centers for Disease Control and Prevention, begged Americans to keep following public health guidelines amid small but alarming upticks in cases, hospitalizations and deaths. “Right now, I’m scared,” she said.

Other scientists tracking the spread of COVID-19 in the U.S. agree that there’s plenty to be worried about. Cases are rising in the Northeast, Midwest and elsewhere. At the same…