City and state officials braced for a potential surge in new Covid-19 cases this week after a long holiday weekend that saw the largest travel volume since March amid a worsening public health crisis.

“In the two weeks leading up to Thanksgiving, our cases [in Boston] were going in the right direction,” Mayor Walsh said on Tuesday. “We may see increases with the impact of the holiday and that’s why it’s important for us to get tested to see if there has been any spread of the virus during Thanksgiving.”

Boston recorded 407 new positive cases on Monday, bringing the city’s caseload to 27,632, a significant increase that Walsh said has his administration concerned.

“We’re going to be monitoring the numbers closely to make sure we don’t see these large spikes,” he said. “That 400 number has been the largest, honestly, since June.” He added: “We have to see what’s going to happen now and I think over the course of the next 10 to 15 days we’ll know what the impacts, if there are any, of Thanksgiving. Hopefully there are none, but, unfortunately, I think there will be some.”

The mayor urged business to allow their employees to work from home if possible— “especially for these next coming weeks in the city as we are starting to see the numbers fluctuate and get a little higher than we’d like to see them,” he said.

Prior to the holiday, the city was seeing another gradual decline in positive cases— even though testing has been happening at a higher volume. For the week ending Nov. 23, the city recorded a daily average of 4,860 tests, up from 4,200 the week before.

“No neighborhoods had a positivity rate over 8 percent, but Dorchester, East Boston, and Hyde Park were over 5 percent,” the mayor said, referring to the pre-Thanksgiving trend. “Every neighborhood saw positivity rates go down in last week’s seven-day average, which is good to see.”

“These numbers do reflect the strong demand for testing ahead of the Thanksgiving holiday. We are encouraged and thankful that everyone got tested. Even though you got tested before Thanksgiving, it’s important for you to get tested after as well,” said Walsh. “Especially if you were a part of large gatherings or came into contact with people you didn’t know.”

The city currently offers free testing at more than 30 locations, including at community health centers and three mobile testing sites.

Also on Tuesday, Gov. Baker raised new concerns about in-person worship in the Commonwealth’s churches, noting that dozens of Covid-19 clusters have developed in houses of worship since the pandemic began, leading to hundreds of confirmed cases of the coronavirus. Faith leaders have responded "admirably," Baker said, implementing creative strategies such as remote or in-vehicle services to limit transmission of the disease.

"But our data still found there are too many clusters that stem from houses of worship,” he said, “ and these cases spread out into the community at large.”

While Baker said he is not asking anyone to avoid churches, temples, and other places of worship, he flagged their role in driving new infections as he stressed taking additional precautions this holiday season.

Services should continue to operate differently, with the pandemic still raging and Massachusetts in the grips of a second surge, he said, and residents should alter holiday plans to emphasize safety — much like he advised ahead of Thanksgiving.

"Recognize and understand that if you're going to get together with people you don't normally spend time with, be safe," Baker said. "Wear the mask. Encourage them to wear the mask. Keep your distance. Wash your hands. Don't share food and beverage. Treat it a little more formally than you might normally."

As of Dec. 1, outdoor dining in the city of Boston is on pause for the winter, but the mayor said that business owners who own private property could extend those programs. “We are working on an aggressive plan to come back strong in April with maybe some new and improved additions to outdoor dining,” he said.

When asked about ending the city’s curfew, beginning at 10 p.m. and extending through 5 p.m., Walsh said he wouldn’t recommend it. “At this particular moment, we have seen two weeks of lowering numbers, but a high number of cases today,” he said. “I think if we can get through the next couple of weeks and get our numbers in the right direction, then we can look at lifting the curfew, but right now it’s not the right time.”