DENVER (KDVR) — A recent increase in COVID-19 cases nationwide is causing concern in communities, especially those with large percentages of unvaccinated people.

The Centers for Disease Control and Prevention found the current 7-day moving average of daily new cases increased nearly 70% compared with the previous 7-day moving average.

In Colorado, case numbers and hospitalizations ticked up in late June for the first time in at least six weeks.

“This is largely a disease of the unvaccinated. The more unvaccinated people you have, the more outbreaks you’re going to have, the more variants you’re going to have,” said Dr. Richard Zane, chief innovation officer for UCHealth.

Zane said people who are vaccinated shouldn’t be concerned about the current Delta variant, a more contagious strain of the virus.

“What we should be worried about is the next variant of the virus after that. All of these unvaccinated people behave as a petri dish: They get infected, more variants come, and they will be responsible for the next variant,” Zane said.

The concern is that vaccines may not be as effective against future variants.

The Colorado Department of Public Health and Environment declared an outbreak following Country Jam music festival in Grand Junction, an area with lower vaccination rates and high case rates of the Delta variant.

More than a dozen rural Colorado counties are currently sitting at or below a 40% vaccination rate.

“It is your societal, patriotic duty to get vaccinated so that we can protect our neighbors, protect the state, protect the country,” Zane said.