Chattanooga COVID-19 cases are on the rise again. Here's what you need to know.

After enjoying a lull in the three months since the last COVID-19 surge, cases are again on the rise in the Chattanooga region.

As of May 19, Hamilton County was averaging 53 new cases per day over the past week, compared to an average of 15 new cases per day at the same time a month ago.

Weekly reports of viral concentration in wastewater are also showing a steady increase, as is the test positivity rate, which has risen from around 5% in early April to 10% in early May and is currently hovering around 15%.

Given the widespread use of at-home testing, which is rarely reported to health departments, Dr. Lisa Smith, medical director for COVID-19 services at One to One Health, said she assumes that for every one case that's reported there are another five positive cases that aren't reported. Based on current data, Smith has started indoor masking again, along with frequent at-home testing and other precautions.

"It's still a deadly disease - not for everybody - but it's still important not to transmit and try to stop the chain of infection, because there are a whole load of people who are vulnerable," Smith said, noting that even though she's up to date with her COVID-19 vaccine and booster shot - meaning an illness would likely be mild - she still doesn't want to become infected and have to miss work.

As a whole, the United States has been experiencing a rise in cases since early April, with roughly a third of the population living in areas that currently meet the CDC's threshold for recommending indoor masking and other precautions.

Hamilton County has not passed that threshold, mainly because hospitalizations remain low, but Smith said "we're definitely in the middle of a little wave." She attributes the fact that there are few seriously ill people to lingering immunity from a combination of previous infection and vaccination.

Smith said now is a good time to restock at-home tests in case you start feeling bad, remembering that if your test is negative it's just a point in time and you should test again if your symptoms don't improve.

The federal government this week reopened its system for U.S. households to order an additional eight free, at-home tests at COVIDTests.gov.

"The emotional end of the pandemic has occurred - everyone's done. But the biological and medical end of the pandemic isn't over," Smith said. "There may be another variant. There may be another wave with waning immunity. We really don't know."

In a news briefing this week, Carissa Etienne, director of the Pan American Health Organization, called for increased surveillance, public health measures and vaccinations to stay prepared for a potential influx of COVID-19 patients as cases are on the rise across the Americas.

Despite having built "incredible networks for COVID testing and genomic surveillance" over the past two years, she said countries are increasingly blind to how the coronavirus is changing and spreading, given that testing rates continue to decline.

"We must keep our eyes on the virus," she said, calling on countries to maintain and strengthen testing infrastructure and to ensure that in places where self-tests are available, results are reported to health authorities.

Contact Elizabeth Fite at efite@timesfreepress.com or 423-757-6673. Follow her on Twitter @ecfite.