IN JULY, the number of COVID-19 cases in Massachusetts increased most dramatically among people in their twenties.

According to state data, people in the 20-29 age category saw their COVID-19 case count go up by 2,064 during July, or about 24 percent of the total increase in cases for the month. On a per capita basis, the 20-29 age category also saw the largest increase of any group.

It’s tempting to conclude from that data that people in their twenties are driving the uptick in the state’s overall case count, which is prompting all the concern that we’re headed backwards on COVID, not forward.

It fits anecdotally, too. Young people as a group tend to worry less about COVID, in part because they’re young and feel invincible and partly because, statistically, if they get the disease they tend to survive. Toss in pictures of young people crowded together, many of them not wearing masks, at Carson Beach in South Boston and it seems like you have all the evidence you need.

Some epidemiologists and health experts are urging the governor to slow the pace of reopening or take it back a notch, although a sharp dip in the number of new cases on Monday made that argument a bit harder to make.

So far, Gov. Charlie Baker has blamed “lapses in judgment” by people attending large parties or gatherings and emphasized the basics – wear masks, social distance, and practice good hygiene. He has also tightened rules a bit on visitors from out of state and warned that additional restrictions may be forthcoming if the case count keeps rising.

One group he has not blamed is the under-30 crowd. “A lot of what’s driving the increase in cases coming out of the South is just an astonishing run-up in positive test rates for the under-30 crowd,” Baker said. “We do not have that.”

Baker said the under-30 crowd in Massachusetts has seen its case count tick upward and its share of new cases increase, but only relative to older age groups that were once sky-high and have now declined.

The 20-29 age group has been fairly consistent, accounting for 14.7 percent of COVID cases on July 31, 14 percent on July 1, 13.4 percent on June 1, and 12.3 percent on May 1.

He said young people in Massachusetts, in general, seem to be following the same precautionary practices as their elders. “Our young people, for the most part, seem to be doing all the same things,” he said.

Bruce Mohl oversees the production of content and edits reports, along with carrying out his own reporting with a particular focus on transportation, energy, and climate issues. He previously worked...