Note: The Delta variant is now the predominant strain of the coronavirus in the D.C. region and across the country. Find the latest information on related increases in local community spread in the Center For Disease Control and Prevention’s COVID tracker. 

The presence of the Delta variant of the coronavirus in the D.C. region is modest, but public health experts say it’s still a significant concern, particularly in communities with low vaccination rates.

“It is more contagious than we’ve seen from some of the other more common variants of the virus,” said Natalie Talis, the population health manager at the Alexandria Health Department. “But it looks like so far that the vaccines that are available are providing protection against that variant.”

The Centers for Disease Control and Prevention has labeled the Delta variant, which was first identified in India this spring, a “variant of concern,” and scientists say there’s some evidence that this new version of the original virus is significantly more transmissible and may cause more severe infection — though there are early indications that existing vaccines provide excellent protection against it.

So far, local public health authorities are reporting a small number of known cases of the Delta variant — also known as B.1.617.2 — in the D.C. region. As of the end of June, 64 cases of the strain had been identified and reported to the Maryland Department of Health. In Virginia, the health department is reporting 67 known cases, including 17 in the Northern Virginia area, as of last week. DC Health did not respond to multiple requests for information before publication.

But those case counts only represent the infections caused by the Delta variant that were tested in the first place, and that were then subject to the lengthier genomic sequencing process to discover the viral lineage.

Genomic sequencing, though, doesn’t happen on every positive test result, meaning there could be additional infections caused by the Delta variant that are not included in the official tallies. In Maryland, for example, about 75% of the positive tests in the last four weeks have been sequenced.

“There could be more instances of that virus around our community that we just don’t know about, because not every case is tested in that way,” said Talis. “We know that it’s here. We know that the Delta variant is here. It’s in Alexandria, it’s in Northern Virginia. It’s in pretty much all of Virginia.”

While the actual number of Delta variant infections in the D.C. region is unknown, officials can still guess at the variant’s prevalence. According to estimates from the CDC, infections caused by the Delta variant of the coronavirus likely make up about 31.4% of the last two weeks’ worth of infections in the Mid-Atlantic region, which includes D.C., Maryland, Virginia, West Virginia, Delaware, and Pennsylvania.

As the Delta variant spreads, Talis said the health department will also monitor overall numbers of COVID cases, hospitalizations, and deaths — all of which have been extremely low in the D.C. region in recent weeks — to see if those trends change due to the more contagious form of the disease.

“We’re looking at all of those numbers to really help guide our our policymaking, as well as guide the information that we share with the public,” Talis said.

Across the country, experts say the Delta variant is well on its way to supplanting the Alpha variant, otherwise known as B.1.1.7, or the U.K. variant, as the dominant strain in the United States. And given that the new strain is highly contagious, experts say that it will likely begin to cause spikes in cases, particularly in communities with lower vaccination rates.

The D.C. region overall has high vaccination rates, and all three major jurisdictions have surpassed the White House goal of having 70% of adults at least partially vaccinated. But racial disparities in vaccinations persist — and the already-large racial gulf in cases and deaths is widening.

And with the Delta variant on the horizon, that gap in outcomes could expand further, with people who aren’t vaccinated extremely susceptible to the disease and people who are fully vaccinated much less likely to get sick. That stratification is already becoming clear, even as the Delta variant emerges: For the month of June, Maryland reported that 100% of the people who died of COVID-19 in the state were unvaccinated, and 95% of the new coronavirus cases occurred in people who weren’t vaccinated.

“The appearance of contagious variants, including the Delta variant, underscore the urgency for all eligible Marylanders to get a vaccine,” a Maryland Department of Health spokesperson wrote in an email.

Local officials have given no indication that they’ll consider reimposing a mask mandate or putting other public health restrictions back in place because of the Delta variant, and the CDC has maintained its stance that masks for vaccinated people are not necessary. (The World Health Organization, in contrast, is recommending that vaccinated people around the globe should continue wearing masks.)

D.C. Mayor Muriel Bowser’s administration has indicated that they will focus on vaccinations, not reimposing restrictions. Asked about reimposing public health measures to protect vulnerable swaths of the population who haven’t yet gotten the shot, Talis said health officials in Alexandria are also concentrating their efforts on overcoming barriers to accessing the vaccine.

“There are definitely policies that would support people, whether or not they’re vaccinated,” she told WAMU/DCist. “But for us, we want to get down to the heart of it and actually just help people get vaccinated so that everyone can have that same level of protection.”

Preliminary research shows that the three vaccines in use in the U.S. — the two-dose Moderna and Pfizer shots, and the one-dose Johnson & Johnson shot — all perform well against the Delta variant, removing a good deal of risk of contracting the disease and all but eliminating the risk of serious illness. The two-shot vaccines, however, produced a slightly weaker immune response to the Delta variant than to the original strain of the virus, and experts are urging people to make sure they get their second shots in order to be fully protected.

Some public health experts have raised questions about whether it would be advisable to recommend people who received the Johnson & Johnson shot get a booster shot of one of the other vaccines. That’s something the CDC is currently studying, and officials from DC Health told Washington City Paper that they won’t make a recommendation until the CDC has more concrete findings to share. In the meantime, there are some early indications that immunity from the Johnson & Johnson vaccine may actually increase over time, and could last at least 8 months.

It’s not just unvaccinated or partially vaccinated people who may be affected with the Delta variant on the horizon. People living with unvaccinated children or immunocompromised family members should still take public health precautions, like wearing masks, washing hands, and social distancing, Talis said.

“There are a ton of families that may have fully vaccinated parents or older adults, but they have children that are under 12 who have not been able to get vaccinated, or they have someone in the family who is immunocompromised,” she said. “And so they still have to be cautious.”