Staff photo by Troy Stolt / Mary Lambert, the new Director of Community Health for the city of Chattanooga, walks a sign that reads "Free COVID Vaccinations No Appointment Required to the corner of Moss drive and through street, just outside of Eastdale Community Center on Wednesday, July 14, 2021 in Chattanooga, Tenn. Lambert has set up an initiative to provide free COVID-19 vaccines at Community and YFD centers across the city.

After enjoying a month of the lowest COVID-19 levels seen since the start of the pandemic, the coronavirus is once again gaining steam in Hamilton County, with the average number of new cases rising more than 250% and test positivity rate doubling in the past two weeks.

The latest resurgence is no surprise to experts, who have been warning that the more contagious delta variant would soon take hold and sweep through pockets of the nation where vaccination levels are low.

Hamilton County's rate of new COVID-19 vaccinations has dropped since mid-April, leaving 58% of the county with only partial or no vaccine protection from the virus, according to data from the Hamilton County Health Department updated on Friday.

Other factors, such as the recent holiday weekend — which local tourism experts said rivaled 2019's record travel figures — and the return of large, in-person activities without face masks are creating ample opportunities for the virus to find its way into susceptible hosts.

"It's that simple. You have a viral strain that is making its way through the United States fairly quickly, and it's approximately 75% more transmissible than the wild-type [original] virus," said Dr. Mark Anderson, an infectious disease specialist at CHI Memorial. "If you have lots of unvaccinated people, they will get infected even easier than with the wild-type virus. And just like the wild-type virus, a certain percentage of them will be super shedders and will spread it to others. So in areas around the country with low vaccination rates, numbers have climbed quickly."

Anderson said the fear is that the Chattanooga region could face a similar fate as parts of Missouri and Arkansas, home of the nation's largest COVID-19 outbreak, if vaccination levels remain low. In several Missouri and Arkansas counties, new case and hospitalization rates have reached or exceeded the same levels as the winter surge.

"I wouldn't say that I know it's inevitable. I'm not a pessimistic, doomsday person. But I think we have a very significant risk of that happening here, and that's going to continue to be the case — other variants are going to come along — as long as large numbers of people decline vaccination. This virus is not going away," he said.

Hamilton County is now averaging 42 new COVID-19 cases per day over the past week with a test positivity rate around 10%, compared to 11 new cases per day and a positivity rate around 5% two weeks ago, according to health department data.

Hospitalizations are also ticking up, particularly among local residents. Of the 26 coronavirus patients in county hospitals on Friday, nine of those were Hamilton County residents. On June 29, there was only one Hamilton County resident hospitalized with COVID-19.

Given the rise of the delta variant, Anderson said residents who are vaccinated and high-risk, particularly people with weakened immune systems, should go back to practicing precautions such as avoiding crowds and wearing face masks in public. Unvaccinated people should always follow those precautions, he said.

Despite the concerning trends, Anderson said another surge would probably not result in as dire of a situation as the winter peak.

"That's what we think, and that's because even though we're under-vaccinated, we do still have large numbers of people who are vaccinated and that includes some of the most susceptible people," he said, such as older adults and nursing home residents.

(READ MORE: Overwhelming number of Tennessee's COVID-19 deaths among unvaccinated population)

The age groups of Hamilton County residents with the highest vaccination rates are those age 71 to 80, followed by 81 and up and age 61 to 70, which are 82%, 74% and 71% vaccinated, respectively.

"'I just keep saying this over and over, and people get tired of hearing it — I would just continue to plead with the people who are not vaccinated to get vaccinated as a demonstration of good citizenship," he said. "We need to work together as a country and look out for each other."

Mary Lambert, director of community health for the city of Chattanooga, said the many organizations working to improve the county's vaccination rates are "chipping away" when it comes to getting shot in arms.

"Every two or three or four is two or three or four more than we had before, and that does move the needle, ever so slightly. But it moves the needle, and we need to do that," she said.

The largest recent gain in COVID-19 vaccinations has been among Hamilton County's Hispanic population, which is now only 3% less vaccinated than the non-Hispanic population.

There are active efforts across the county to bring vaccinations to underserved groups — such as Hispanics— because they're more likely to face barriers to medical care, including a lack of transportation or distrust in the health care system.

Contact Elizabeth Fite at or follow her on Twitter @ecfite.