Phoenix Mayor Kate Gallego (D) attributed soaring case numbers in Arizona to the state’s decision to resume business as usual before the virus was under control. She noted that young people who ignored health precautions had probably led the explosion in cases.

Gallego said federal officials had dismissed her requests to conduct community-based testing in the area after people reported waiting in line for six hours at some testing sites. “We were told they’re moving away from that,” she said, “which feels like they are declaring victory while we’re still in crisis mode.”

The local officials said mixed messages about reopening contributed to a false sense among the public that the crisis had passed. “The city of Miami was the last city in the entire state of Florida to open. I was criticized for waiting so long,” Suarez said. “But there’s no doubt that the fact that when we reopened, people started socializing as if . . . the virus didn’t exist.”

The number of deaths and the morbidity rate have not increased with the surge in new cases, in part because the spike in infections has been among younger, more resilient victims. And health officials say they now know more about the disease than they did when deaths were on the rise.