Boston stands at a crucial inflection point in the pandemic’s latest surge, and the arc of case growth over the next few days could determine whether city leaders reinstate a near-total shutdown, Mayor Martin Walsh warned Thursday.

In Walsh’s view, the city has already deployed almost every resource and strategy — a curfew, a mask mandate, shuttered school buildings and more — it can to combat the spread of the highly infectious coronavirus.

But in the wake of the Thanksgiving holiday, new statewide case numbers reached a record high on Wednesday while Boston is counting new infections at a rate not seen since the spring.

Those figures pressed Walsh to caution on Thursday that, depending on how the trend moves, the “last resort” option of shutting everything down may come into consideration as soon as next week.

“The next step is shutting everything down. That’s the next step,” Walsh said at a press conference. “We’ve done that before and, you know, we’re three weeks away from Christmas, our retailers need people to go in and shop in, our restaurants need people to eat in, people are working and they need to make money. That’s the last resort, shutting things down.”

“But if these numbers continue to go up and we see, maybe Tuesday, I’m standing here, I could be talking about putting plans down for shutting things down,” he continued. “Hopefully, Tuesday, I’m talking about seeing the numbers go the other way again.”

Boston recorded more than 400 new COVID-19 cases in each of the past two days, some of the highest daily infection totals in months. Since Friday, about 70 more patients have been admitted to Boston-area hospitals, which Walsh said is particularly concerning.

Last week, Walsh said the data had been heading in the “right direction” and voiced hope about starting to plan to shift from remote to in-person learning. The latest “significant uptick,” however, changed that thinking.

“Three, four days ago, we were talking about opening schools and keeping restaurants open, and today, it’s in the back of our mind,” he said.

Most students in Boston public schools have not been inside their schools since mid-March.

Walsh directly linked the spike in confirmed cases over the past few days to Thanksgiving.

While many followed the guidance of elected officials and health experts and kept the holiday celebrations to their immediate families, “other people traveled, other people had gatherings at their house, and we’re seeing the impact,” Walsh said.

Getting tested ahead of Thanksgiving travel is insufficient on its own, the mayor argued. Instead, anyone who traveled or hosted gatherings on the holiday should get tested in its wake as well.

City officials are still working with state leaders to determine a process for distributing a vaccine and which residents will be at the front of the line. Gov. Charlie Baker said Monday that the first immunizations could arrive this month.

In the meantime, Walsh reiterated familiar guidance: wear a mask, keep distant from others as much as possible, practice good hygiene, and quarantine after possible exposure. Anyone over the age of 65, he said, should not go to restaurants or other spaces where risks are higher.

The Baker administration again stood up a field hospital in Worcester, and officials said Thursday they plan to open a second one in Lowell.

Asked about plans to reopen a field hospital in Boston, Walsh replied, “Worcester two weeks ago, Lowell this week, I mean, we’re right behind.”

“We’ll get it up quick. We did it in five days last time,” Walsh said. “But I think it goes back to a question that was asked earlier. By Tuesday, we could be building a field hospital, or by Tuesday, we could be talking about numbers getting better in this region.”