Health officials reported Friday that the county's coronavirus positivity rate has slowly increased from below 1% up to 3.4%.
Fresno County's interim health officer Dr. Rais Vohra said it's a marker that things are sliding in the wrong direction.
"If nothing else has changed, if we haven't started doing more testing and if we're not doing more selective testing, then why is the positivity rate going up? Well, one explanation is that we have a variant that's more contagious and is now being found in more and more people," said Dr. Vohra said.
As of Friday, Vohra said the county currently has 30 cases of the Delta variant, up from the 22 cases that were reported on Thursday.
Vohra said that number is likely higher because of low testing rates and a delay in variant testing.
"We may be in for some turbulence as this Delta variant takes off in the county," he said.
RELATED: Fresno County officials recommend everyone wear masks, even if vaccinated
The interim health officer added that the Delta variant is mostly circulating through unvaccinated people.
On Thursday, Fresno County health officials "strongly recommended" all people still wear face masks indoors regardless of vaccination status as more Delta variant cases are reported.
Health officials said while there is no single protection for COVID-19, vaccines and mask-wearing provide significant protection against the Delta variant and all other COVID strains.
Vohra said hospitals are also seeing more COVID patients. Fresno County has around 57 people who are currently hospitalized with COVID-19. That includes those who have contracted the Delta variant.
"I would say more than 90% (of the COVID hospital patients) are non-vaccinated or partially vaccinated, so they're not fully vaccinated yet, and they catch the coronavirus," he said.
The patients ending up in the hospital are also shifting toward a younger population as more and more of high-risk and older groups receive their vaccines, health officials reported.
As the test positivity rate increase, there's a concern for the potential strain on healthcare workers.
Dr. Vohra said it's "all hands on deck" when it comes to keeping case rates down in the county.
"If we want to keep this virus under control and really don't give it a chance to create new mutations, we need more people vaccinated," Dr. Vohra said.