A little more than two months after D.C. lifted its mask mandate, Mayor Muriel Bowser announced Thursday that masks will once again be required in all indoor settings, starting Saturday, July 31.

The new order will apply to all individuals over age two – regardless of vaccination status — at all indoor businesses, including gyms and restaurants.

“We do not have an exception for any type of indoor venue,” DC Health director LaQuandra Nesbitt said during a press conference Thursday.

The new mask guidance did not come with a rollback on any business or travel restrictions — meaning all restaurants can remain open at full capacity with no social distancing requirements, but all staff and patrons will need to be masked when they’re not eating or drinking. Nesbitt also recommended that fully vaccinated individuals who live with unvaccinated children or immunocompromised people resume wearing masks in crowded outdoor settings, for example Nationals Park and Audi Field.

The city’s order follows new guidance from the Centers for Disease Control earlier this week, which directed all individuals, regardless of vaccination status, to wear a mask indoors if they live in a part of the country with “high” or “substantial” virus transmission. Nearly two-thirds of the country fits that definition.

As of Wednesday, D.C. reached the point of “substantial” community spread, per the CDC.  “Substantial” transmission occurs in any locality that reported 50-100 new cases per 100,000 residents over the past week, or is reporting a positivity rate between 8% and 10%. According to the CDC’s website, D.C. reported 52 new cases per 100,000 residents in the past seven days, and the District’s positivity rate stands at roughly 2.6%.  D.C. is currently reporting a seven-day average of 59 new cases a day — a six-fold increase from the beginning of July, and the highest that metric has been since early May.

Nesbitt said the recent increase in infections can be attributed to a younger cohort of residents, between the ages of 5-14 and 20-34. Through contact tracing, Nesbitt said officials have linked activities like domestic and international travel, dining out, and large social gatherings to the spread of the virus. She did not provide updated information on vaccine “breakthroughs,” or infections in vaccinated residents, but the city’s most recent data (which was last updated on July 11), show that roughly 36% of the 200 breakthrough cases reported since January occurred in individuals ages 30-49, and 17% occurred in individuals ages 18-29. Nesbitt encouraged fully vaccinated residents to wear a mask when they are in private, indoor social settings, if they are around guests with unknown or mixed vaccination statuses.

Bowser said the new mask mandate does not change the city’s posture on workplace reopening or return-to-office plans.

“We continue tell people to come to their offices and that we’re open, just like we have been in D.C. government,” Bowser said. She also stated that the city is working with “labor partners” to develop a vaccination requirement for city government workers. 

While the Delta variant accounts for the majority of new infections in the U.S., Nesbitt said on Thursday that the variant makes up less than 5% of the case samples sequenced by the D.C. government, but there are certain factors that limit how many samples are sequenced. She said officials remain “laser focused” on tracking the Delta variant and boosting labs’ capacity to test more samples.

While the city’s public health emergency expired on Sunday, Bowser extended its public emergency, which allows her to retain certain powers, like a mask mandate. When asked Thursday whether more restrictions are on the way, Bowser said she hopes the new mask guidance in addition to vaccinations “stops [the case increase] before it goes too far.” Roughly 50% of the city’s total population is fully vaccinated.

“What I’ve learned with this virus is that you have to go with what the virus is doing in the country,” Bowser said. “We feel very good about what we’ve been able to accomplish here, crushing the virus and getting people vaccinated, but we are not a bubble in the world.”

Regionally, Alexandria City has also recommended that its residents resume wearing masks in indoor public spaces, after the city fell into the “substantial” transmission zone on Tuesday. Loudoun County’s transmission’s rate is also substantial, but officials have not yet announced an updated mask recommendation. Meanwhile, as Bowser updated D.C.’s mask guidance Thursday, Virginia Gov. Ralph Northam recommended — but did not mandate — that residents resume wearing masks in indoor public settings.

This post has been updated with additional information.