The city of Philadelphia announced Monday that mask mandates will be reinstated next week, less than a month after they were lifted across the county, citing a 50 percent increase in reported COVID-19 cases in the last ten days.

“It’s commendable that they’re taking the initiative,” says the author “Abby Rudolph, an associate professor of epidemiology and biostatistics at Temple University in Philadelphia, echoed these sentiments. “Many people are testing at home, and we aren’t recording all of them. When we do see an increase, it’s most likely to be a little higher than what’s reported.”

While the city is the first to reinstate mask laws this spring, it isn’t the only place where cases are on the rise. According to a Johns Hopkins analysis of data, national weekly case counts have risen to over 245,000, up from below 200,000 at the start of the month.

Public health officials say they’re keeping an eye on the situation but aren’t concerned – yet.

Dr. Ashish Jha, the White House COVID-19 response coordinator, said Monday, “I’m not overly concerned right now.” “I believe we must exercise caution, but I do not believe we must be overly concerned at this time.”

The majority of the increases are concentrated in Northeastern states with high vaccination rates, such as Vermont, Connecticut, Rhode Island, and New Jersey, as well as Washington, D.C.

According to public health experts, these states and the District of Columbia were among the first to be hit by the original omicron variant earlier this year, and residents were among the first in the country to be vaccinated and boosted. Immunity from vaccination and previous infection may have worn off, leaving them vulnerable to the BA.2 variant and leading to an increase in cases.

On Sunday, White House chief medical adviser Dr. Anthony Fauci told “This Week” co-anchor Jonathan Karl, “This is not unexpected.” “We’re going to see an uptick when you have a highly transmissible virus like BA.2 and you’re pulling back on mitigation methods at the same time there’s waning immunity.”

Increased cases, according to Fauci, will not lead to more hospitalizations or deaths, but some health experts believe that depends on how states respond.

“The CDC mask mapping numbers are important for preventing overburdening hospital infrastructure, but we may need to consider masking in a slightly different way to keep cases down,” said Jodie Guest, professor and vice chair of Emory University’s Rollins School of Public Health’s department of epidemiology.

Because most transmission occurs in private gatherings rather than public spaces, Rudolph is skeptical that mask mandates will stop the rise in cases. But, she said, it’s better than nothing. “It’s the weakest line of defense we have,” she explained. “We want to be proactive rather than reactive so that we can avoid the worst consequences.”

Guest also urged people to get a COVID-19 booster and to consider getting a second one if they are eligible. Last month, the Food and Drug Administration and the Centers for Disease Control and Prevention approved second boosters for anyone over the age of 50.

For those with a healthy immune system, scientific research doesn’t offer much guidance on a fourth shot, but Guest said the decision to get a second booster is a personal one, and the risks of getting COVID-19 outweigh any risks from the shot.

“It has no drawbacks,” she stated. “If you work in health care, if you live with someone who is immunocompromised, or if you live with a child who cannot be vaccinated, these are all good reasons to get it.”

If mitigation measures remain minimal, health experts predict that cases will rise across the country, but it’s unclear whether this will result in another surge or a gradual decline.

“The next month will be extremely important to watch,” Guest said. “It’s critical to keep (masks) in the forefront of people’s minds.”