The highly contagious delta variant is the dominant version of the coronavirus in Virginia and Maryland and is expected to be on the rise in D.C., but officials so far say they have no plans to reinstate mask mandates and social distancing restrictions just as the economy is rebounding.

Instead, public health experts are focused on getting people inoculated against the virus. But vaccination rates are stalling throughout the region, and testing — which is key to understanding the spread of variants — is down sharply from earlier in the pandemic.

While restrictions lifted around the country and locally weeks ago, some jurisdictions have reimposed limits over concerns about the delta variant or a rise in cases in general.

In California last week, Los Angeles County reinstated a mask mandate, and Bay Area health officers recommended mask-wearing indoors, while masks are being discussed again in states such as Arkansas and Missouri, where cases are spiking.

The delta variant has become the dominant strain of coronavirus in the United States, resulting in a rise in infections and hospitalizations. (John Farrell/The Washington Post)

Ahead of a return to in-person school in the fall, the American Academy of Pediatrics recommended this week that everyone over the age of 2 wear masks, even if they are vaccinated.

Meanwhile, cases are on the rise in the Washington region, although the numbers are still significantly below local spikes fueled by the alpha variant in the spring.

Across the greater Washington region, the seven-day average of new cases on Tuesday was 629, the highest it’s been since May 28.

In Virginia, the seven-day average of new cases was just over 5 per 100,000, the highest since May 21. In D.C., it was 5.95, the highest since May 19, and in Maryland the figure was 2.61, the highest since June 2.

Virginia has identified 158 ­cases of the delta variant as of Friday, with the biggest share in the central part of the state, followed by Northern Virginia, according to the state Health Department.

The alpha variant, first discovered in the United Kingdom, was the dominant strain in Virginia through March and April, but the share of the delta variant has steadily increased, state data shows. For example, in the week ending July 3, the state identified six cases of the alpha variant but 15 cases of the delta variant, turning the tide toward the highly contagious version.

That trend is worrying public health officials in regions with pockets of unvaccinated residents.

“We’re very worried. We’ve had a few of the delta so far,” said Karen Shelton, director of three health districts representing all of Southwest Virginia, which is heavily affected by case trends in bordering states.

“When we see northeast Tennessee starting to surge, in just a few weeks, Southwest Virginia does,” she said.

Maryland has identified 90 cases of the delta variant as of July 12, including eight cases that required patients to be hospitalized, according to the state Health Department.

Most cases are in the populous Washington-Baltimore area, Jinlene Chan, the deputy health secretary said, adding that it has been detected in rural parts of the state, as well.

In D.C., the delta variant made up just 1 percent of tests sequenced recently by the city lab, according to Patrick Ashley, head of emergency response in the D.C. Health Department. But he anticipated that will change.

“Frankly, it’s somewhat of a matter of time before we see that 1 percent number grow,” Ashley said.

Area leaders say they have no plans to bring back the restrictions or mask requirements from earlier in the pandemic, instead urging the unvaccinated to get the shots.

The Centers for Disease Control and Prevention tracks variants by region. For the region including Maryland, Virginia, and D.C., as well as Pennsylvania, West Virginia and Delaware, the delta variant made up 12 percent of cases in the two-week period ending June 19.

The rate is low compared with areas hit hardest by the variant, such as the region including Iowa, Kansas, Missouri and Nebraska, where it represents 75 percent of new cases and vaccination rates have lagged behind the rest of the country.

But testing is also down, meaning there are fewer positive tests to sequence — and detect whether a variant is present — than earlier in the pandemic, when more people were seeking tests.

Virginia, for example, reported 6,512 coronavirus tests taken on Monday, compared with 24,000 in mid-March.

Even among positive samples, labs are constrained by the quality and age of the sample, as well as the viral load contained in it.

Since the start of the pandemic, 1.58 percent of positive tests have been sampled in Virginia, and 3.3 percent of positive tests have been sampled in Maryland, CDC data shows.

Both states are using their public health labs and relying on a network of hospital and university labs, as well as private labs.

D.C. has the capacity to sequence 100 specimens every week to check for the delta variant, Health Director LaQuandra Nesbitt said. That means the lab has been able to sequence every positive test in the District for the past several weeks.

Luke Tallon, scientific director of genomics at the University of Maryland School of Medicine, said with fewer cases, there are fewer positive tests to analyze for variants.

“We always want more data and would always like to sequence more samples. The biggest challenge right now is, testing volume is really low. There’s not as many people testing positive, so we don’t know how many people out there are asymptomatic and not being captured and sequenced.”

Public health officials are encouraging anyone experiencing symptoms, whether they are vaccinated or not, to get tested.

“The more testing we do, the better we’ll be able to answer these questions,” Tallon said.

Jacqueline Dupree and Julie Zauzmer contributed to this report.