Health and Human Services Secretary Alex Azar said Monday a continuing surge in coronavirus cases in Arizona and across the nation can be attributed to a lack of responsibility among younger people.

Azar said that the average age of infected individuals has continued to fall in recent weeks.

That trend includes metro Phoenix, where the percentage of positive reported tests in people between the ages of 20 and 44 has jumped from 49% to 53% in the past three weeks.

“Certainly there’s a behavioral element to it that we cannot deny as we’ve seen the average age of positive-tested individuals go down dramatically,” Azar said.

Azar thinks the spread is increasing among young people because they’re the ones who have flocked to bars and large social gatherings since states have reopened.

He said health officials are adjusting their prevention strategy in order to get through to those who may not think much of the virus because of their age.

Azar said it’s important for younger people to recognize that even if COVID-19 isn’t potentially harmful for them, it could be for others.

“They could put others very much at risk around them,” Azar said. “People that they care deeply about or strangers they run into.”

State leaders have had to pull back on reopening plans in recent weeks because of increased case totals.

Gov. Doug Ducey ordered gyms, bars, nightclubs, movie theaters and water parks to shut down June 29 for at least 30 days.

In Arizona, coronavirus cases passed 100,000 on Monday.

“We’re there to support. We made it clear to Gov. Ducey that we will be there to back you all up, but it’s going to take the whole community taking action,” Azar said. “This is a very serious situation.”