Driven by delta variant, Denver's COVID-19 numbers see sustained increase

Denver's COVID-19 case numbers have climbed in recent days, the first significant, sustained increase in weeks that's being driven by the delta variant.

The city has averaged 47.7 new COVID-19 cases per day over the past week. That's still far below any previous peak, and hospitalizations have yet to spike. But it's driven the city back to its early June average, and officials "have every reason to believe that this is related to the new delta variant ... which is more contagious," said Denver Health's Seth Foldy. He said the variant now accounts for 90% of Colorado's new cases.

"This is not just a wrinkle in the data," he said Friday. Though it's too early to tell what the short and mid-term situation will look like, Foldy said he would "expect to see changes" to the city's COVID-19 response, meaning mitigation efforts that have largely been abandoned here since the late spring. "But it's too early to predict," he said, which changes may be implemented.

He added that "it may be reasonable for people to rethink their attitude about going indoors with large numbers of people they don't know ... and it might make sense for us to be wearing masks more freely indoors during a period of this uncertainty."

Denver is far from alone in seeing a spike. Like the nation as a whole, Colorado has seen its numbers grow consistently for days. The state is now averaging 521 cases per day over the past week, the most since May 31. The average positivity rate has also consistently climbed of late, and as of Friday evening, it stands at just over 4%, the highest average since May 18.

Earlier Friday, the Tri-County Health Department said in a statement that cases in Douglas, Arapahoe and Adams counties were also increasing. That's "especially concerning," the agency wrote, "with school beginning in the next few weeks." The cause of the spike there is the same as it is at the state and city level, officials have said: a portion of the population is still unvaccinated, and the delta variant is more transmissible and more severe.

In "Adams County, the 7-day incidence rate per 100,000 for COVID-19 cases was 69 per 100,000," Tri-County Health wrote. "This represents an increase of 155% since June 26. Arapahoe and Douglas County have experienced increases of 70% and 65% over the same period." 

Both Foldy and Tri-County said that the majority of the new cases are among the unvaccinated, a population that has proved to be a breeding ground for delta.

"It's so contagious that if you're in the middle of a crowd and you've not been vaccinated, it will find you," Foldy said. 

Denver's vaccination rate is among the best in the state. According to state data, more than 75% of the city's eligible population has been at least partially vaccinated. Foldy said there have been breakthrough cases - meaning infections. within vaccinated people - but that the vast majority are among the unvaccinated. 

He said it was "too soon" to tell if the All-Star Game has exacerbated the situation, though he said the Fourth of July likely played a role. The All-Star Game "is one of many events that have brought people in closer proximity over the last several weeks."

Foldy referred to a recent modeling group used by the Centers for Disease Control and Prevention projected "a nationwide rise in cases that persists at least to October." 

"If you’re sitting on the fence wondering about vaccination, the time to get vaccinated is now," he said. "If delta finds you, you’re going to get sick. If delta finds you, you’re going to transmit the virus to others. If you get vaccinated, the risks of those things happening go way down."