Chicago is now averaging more than 400 new COVID-19 cases per day — a number the city’s top doctor once called “a line in the sand for us.”

While that number was previously used as a harbinger for when to institute — or remove — mask mandates, local doctors now say it’s an imperfect metric, in part because many people don’t report positive at-home tests and vaccines are widely available.

Philadelphia officials on Monday became the first in a U.S. city to reinstate an indoor mask mandate after cases there rose more than 50% in 10 days, according to the Associated Press. Will other cities follow their lead?

In Chicago, cases rose 41% compared to last week, but experts say there are reasons to be hopeful. Hospitalizations remain low and the highly contagious BA.2 variant has been present in the city for months without a surge similar to prior strains like omicron and delta.

Warmer weather may also help. “We’re coming out of the time of year when the seasonality really provides an advantage to the virus,” Dr. Emily Landon said.

With more workers returning to offices this month, spring travel underway and holiday gatherings slated for this week, we asked Chicago doctors to help put the recent increase of COVID-19 cases in context. Here’s what you need to know about where things stand.

Does the 400-case metric still matter?

Landon, an infectious disease specialist at the University of Chicago, said “one metric is never going to be enough.”

“I think the reality is that the [meaningfulness of the] numbers of cases over time in the pandemic is going to change,” she said.

While the number of how many people actually have COVID in Chicago right now is surely higher than the 428 daily case average being reported, Landon said it still doesn’t mean officials need to rush to put additional mitigations in place.

Landon said a tailored response makes more sense for this stage of the pandemic.

The numbers that officials use to make decisions has already changed. The Illinois Department of Public Health announced this week that it will follow new federal guidelines that don’t require providers to report negative tests. That means the department will no longer report the state’s case positivity.

Will a mask mandate return in Chicago?

Landon thinks at some point masks will again be used in Chicago to prevent the transmission of disease.

She predicted mask mandates will return with seasonality, saying she sees a “very high” likelihood that “we’re going to be wearing masks next year in the middle of winter.”

Dr. Michael Angarone, an infectious disease specialist at Northwestern Medicine, also said it’s likely public health officials will turn to mask mandates again, but the threshold must be determined.

“What point do you say, let’s start wearing masks again, versus just continuing as usual? I think that’s a really hard kind of threshold to pick,” he said. “And I think that’s something that the public health organizations have to determine.”

Where do COVID-related hospitalizations stand right now in Chicago?

Angarone said it’s important to look at the number of hospitalizations “because that tells us, are people getting much sicker with coronavirus?”

For now, “the hospitalizations are very low,” Landon said. According to city data, hospitalizations are down 17% from a week prior. But Landon said she would be surprised “if we don’t see an uptick in hospitalizations in the next couple of weeks.”

“How high it’s gonna go, how bad it’s going to be, is still unknown to me,” Landon said.

Dr. Mia Taormina, an infectious disease specialist with Duly Health and Care, told WBEZ’s Reset that “fortunately” a lot of people most vulnerable to severe illness and infection have been fully vaccinated and boosted, which may help to keep hospitalizations from rising significantly.

“I do have a handful of patients in the hospital currently, but nothing like what we’ve seen before,” Taormina said.

Is this the beginning of another surge?

“Nothing is showing me that we’re going to have some overwhelming surge,” Taormina told Reset.

Taormina said she expects the number of new cases will continue to ebb and flow over the months to come, until we reach the fall, when “we will see numbers probably come up a little more substantially.”

Landon noted that BA.2, a subvariant of omicron, has been present in Chicago since February.

“In some countries [BA.2] causes a surge, but it has been in Chicago, and it’s had every opportunity to do so and it hasn’t done one of these fast, rapid-rise surges,” Landon said.

What can individuals do to protect themselves right now?

Just because Chicago may not be in for another surge, Landon notes that “doesn’t mean that a lot of people aren’t going to get COVID.”

“It doesn’t mean that your family isn’t going to get infected with COVID or that you don’t need to wear a mask, it means that we need to be cautious and tailor our response,” she said.

Angarone recommends taking precautions in situations when you don’t know who has been vaccinated or what people’s exposures are. He suggests the strategies we’ve become familiar with like: wearing a mask, keeping your hands clean, not touching your face with your hands and trying to keep yourself distanced from other people.

Landon advises people to think about taking added precautions when it comes to “the three Cs”: closed spaces, close contacts and crowds.

In a work setting, that may mean feeling comfortable without a mask in a large space, but putting masks on when meeting with others in an enclosed office.

Ultimately, Landon said “there is no strategy that is going to be zero risk.”

Courtney Kueppers is a digital producer/reporter at WBEZ. Follow her @cmkueppers.