SANTA ANA (CNS) — Orange County's weekly COVID-19 averages released Tuesday showed a sharp increase in cases, largely due to the delta variant, which has been characterized as a "game changer" by one local expert.

According to the latest weekly averages released Tuesday, Orange County's average daily case rate per 100,000 residents increased from 4.9 to 8 in a one-week period, and the test positivity rate jumped from 3.3 to 4.9%.

The county's Health Equity Quartile rate, which measures the disadvantaged communities hardest hit by the pandemic, increased from 3.4% to 4.4%.

The positivity rate is more alarming as it reflects more people being infected rather than an increase in testing, said Andrew Noymer, an epidemiologist and UC Irvine professor of population health and disease prevention.

"Delta is exploding everywhere," Noymer told City News Service. "It's become apparent Delta has become a big game changer."

Orange County reported 453 new cases of COVID-19 Tuesday, along with another increase in hospitalizations. 

The number of coronavirus patients in county hospitals was 212, up from 194 on Monday, according to the Orange County Health Care Agency. There were 48 COVID-19 patients in intensive care, unchanged from Monday.

The county had 27% of its ICU beds available as of Tuesday.

One additional coronavirus death was also reported. Tuesday's figures brought the county's cumulative total to 262,524 cases and 5,140 fatalities since the pandemic began.

The death toll for July is 2; 15 for June; 22 for May; 43 for April; 199 for March; 612 for February; 1,563 for January — the deadliest month of the pandemic — and 967 for December, the next deadliest.

Noymer expects fewer deaths during this surge because of high vaccination rates among seniors.

The delta variant is a great deal more contagious and produces higher viral loads, but it is not clear how much more deadly it could be, Noymer said.

"It's not clear to me that delta is more deadly, but it is clear to me it's more spreadable," Noymer said.

The rising level of breakthrough infections are concerning, Noymer said. The vaccines are effective at keeping most recipients from hospitalization or serious illness, but Noymer pointed out he is acquainted with two fully vaccinated people who were hospitalized for a COVID-19 infection.

"It's not a crisis, but the direction of travel is backwards and that is the issue," Noymer said. 

As for the new Centers for Disease Control guidance that even vaccinated people should return to masking indoors, Noymer said he endorsed that.

The most dominant variants in Orange County in recent weeks have been the delta, alpha and gamma variants, according to the OCHCA. Delta and alpha are considered much more highly contagious, with delta now considered the most dominant strain statewide.

Experts say the current COVID vaccines all provide a high degree of protection against infections and — while they will not prevent all infections — they usually prevent serious illness and death.

As of Thursday, the county reported that 1,876,853 residents were fully vaccinated. The number of residents who have received Pfizer or Moderna and are fully vaccinated is 1,754,729, and the number of those who received the one-dose Johnson & Johnson vaccine and are fully vaccinated is 122,124.

The county reported there were 214,245 who have received at least one dose of the two-dose Pfizer or Moderna vaccines.