COVID-19 is increasingly a disease of the young, with the message to stay home for the sake of older loved ones wearing off as the pandemic wears on.

The dropping age of the infected is becoming one of the most pressing problems for local officials, who continued Wednesday to set curfews and close places where the young gather. U.S. health experts say that they are more likely to be active and asymptomatic, providing a vast redoubt for the coronavirus that has killed almost 130,000 Americans.

In Arizona, half of all positive cases are people from the ages of 20 to 44, according to state data. The median age in Florida is 37, down from 65 in March. In Texas’s Hays County, people in their 20s make up 50 percent of the victims.