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Dropping masks could have an unintended side effect: the return of sniffles and stomach bugs

As mask recommendations are loosened in Massachusetts and other parts of the country, doctors expect to see a resurgence of non-COVID infections this spring

A woman sneezes after getting a nasal swab for a rapid COVID-19 test at a community medical center in Sao Paulo, Brazil, Friday, Jan. 7, 2022.Andre Penner/Associated Press

The long-range forecast for this spring includes a lot of sniffles.

Two years of wearing masks, avoiding crowds, and trying not to catch COVID-19 had a welcome, if unplanned, byproduct: many people caught fewer colds and stomach bugs. But that could soon change. At the end of the month, Massachusetts will no longer require masks in schools and has dropped its recommendation that healthy vaccinated people wear masks indoors. Doctors say that means we should brace ourselves for the return of common infections many people have blissfully dodged for the past two years.

“You will see a lot of anecdotal reports that the primary care offices and urgent cares are a little slammed,” said Dr. Christina Hermos, a pediatric infectious disease specialist at UMass Memorial Children’s Medical Center.


Social measures to prevent the spread of the coronavirus have disrupted the transmission of many common pathogens around the world, most notably the flu. The flu virus barely made an appearance last winter and is still markedly lower than normal this season. Viruses that cause common colds and stomach flu have also been curtailed, to varying degrees.

But as people resume social activities, doctors and scientists don’t expect the respite to last.

“I will not be surprised if we see an increase in infections from respiratory viruses as we lift our mitigation measures,” said Dr. Sabrina Assoumou, an infectious disease physician at Boston Medical Center and professor at Boston University School of Medicine.

Studies from other states and countries illustrate how quickly common pathogens return when COVID restrictions are lifted. For instance, researchers at Houston Methodist Hospital in Texas found that infections of respiratory syncytial virus and some common cold viruses shot up after Texas Governor Greg Abbott in March 2021 opened businesses to full capacity and banned government mask mandates in the state.


Earlier this month, researchers in Israel reported that non-COVID respiratory infections and gastrointestinal infections were 2.6 times more likely in young children in the few months after mask mandates and social restrictions were ended in spring 2021, compared to before the pandemic. Respiratory infections were 1.7 times more likely for all age groups.

In most cases, doctors say, the return of common sicknesses will likely present more of a nuisance than a crisis. “I don’t think it is cause for concern,” said Dr. Philip J. Landrigan, pediatrician and epidemiologist at Boston College. “It is just back to the unpleasant situation that we had to deal with every winter before COVID-19.”

Pediatricians say it’s normal for children to get infections at different rates. Those who don’t go to day care may encounter fewer germs early in life, but their immune systems can catch up when they enter kindergarten, Hermos said.

“There are many illnesses that are rites of passage in childhood,” she added. “There’s no reason to think that the routine illnesses of childhood would be more severe just because they’ve been delayed.”

Hermos also is not concerned about adult immune systems weakening after two years of sheltering. “There isn’t a reason to think that our immune systems have wasted away and minor illnesses will suddenly be more difficult to deal with,” she said.

With the potential exception of the flu, where annual boosters are recommended, scientists say people shouldn’t worry about losing immunity from vaccines they received before the pandemic.


“Most of the vaccines that we have don’t necessarily need reinforcing infections to keep the immunity going,” said Dr. Walter Orenstein, associate director of the Emory Vaccine Center in Atlanta.

A bigger concern is making sure children get up to speed with their childhood immunizations, as many fell behind schedule during the pandemic, he added.

People may have lost some immunity to common cold viruses, but infectious disease doctors are not concerned since immunity to those viruses is short-lived and reinfections are common.

Immunity is also short-lived for bugs that cause gut infections, such as norovirus or salmonella, said Dr. Dean Blumberg, chief of the division of pediatric infectious diseases at UC Davis Health in California. He isn’t anticipating a post-pandemic spike in those pathogens. “If people go on more cruise ships, there will be more norovirus, but I don’t think it will be twice as much as before the pandemic.”

The Centers for Disease Control and Prevention estimates there have been up to 3.8 million flu illnesses and as many as 3,700 flu deaths so far this season, a fraction of the average 30 million illnesses and 36,000 deaths per season in the decade before the pandemic. As of Feb. 18, the CDC rated all states as having “low” or “minimal” influenza activity, and the Massachusetts Department of Public Health said that flu cases peaked in late December 2021 and have since fallen to low levels.

It might be a different story next winter. Because so few people have developed natural immunity to the current circulating strain, H3N2, and fewer people received flu shots this year, the next flu season could be more severe if people aren’t wearing masks, said Dr. Stanley Plotkin, professor emeritus of pediatrics at the University of Pennsylvania.


“If you get infected with H3N2 this winter you will likely be immune for a couple of years but eventually you will be susceptible again,” Plotkin said. And for people who haven’t been infected or vaccinated in a couple of years, “that may be the situation now.”

Doctors are also watching for a rise in respiratory syncytial virus, or RSV, which infects most children in their first three years of life. RSV cases have been low during the pandemic, although there was an unseasonal surge in late summer and early fall of 2021. Dr. H. Cody Meissner, chief of the division of pediatric infectious disease at Tufts Children’s Hospital, said RSV infections could increase as COVID restrictions are eased, but he isn’t worried.

RSV is most dangerous and causes the most hospitalization in the first six months of life, Meissner said. That is because inflammation in an infant’s airways, which are about the size of a thread, can make them very sick. Once the airways in their lungs get bigger after 12 months of age, the inflammation is less life-threatening. Infants who weren’t exposed to RSV during the pandemic will likely still get infected, but at an age when the disease is usually less severe, Meissner said.


But more people infected with RSV at once could be bad news for the youngest infants ― those most vulnerable to the virus ― and for older adults whose immune systems are sometimes unable to fend off the virus. There is no vaccine for the virus yet, although several companies are developing one.

Some common infections have already begun returning to Massachusetts this winter. Dr. Jonathan Hatoun, a primary care pediatrician at Boston Children’s Hospital, and his colleagues have analyzed electronic health care records of children in Massachusetts to track how diagnoses of 12 common infections changed after social distancing and mask wearing began in March 2020.

Unpublished data Hatoun shared with the Globe shows that bronchiolitis, common cold, croup, influenza, middle ear infections, pneumonia, sinus infections, stomach flu, and strep throat remained low — and almost nonexistent in some cases — throughout 2020 compared with the previous year.

That’s started to change this winter. Some viral infections, including common colds and stomach flu, rose to pre-pandemic levels. Bacterial infections, including ear and sinus infections, were slightly more frequent this season, but still lower than pre-pandemic levels, and cases of strep throat were still almost “nonexistent,” Hatoun said. It matches what he sees in the clinic. “We are writing less antibiotic prescriptions.”

“Wearing masks, social distancing, intense hand washing, and air filtration in schools have definitely reduced common pediatric infections and any walking back of those is likely to increase the frequency of those same infections coming back,” Hatoun added.

He cautioned the data could be skewed, as some parents might be more likely to go to the doctor to make sure their children don’t have COVID, or conversely, avoid visiting altogether out of fear of catching it.

Dr. Kristin Moffitt, a pediatrician at Boston Children’s Hospital who specializes in infectious diseases, noted that before the pandemic, most people with mild respiratory infections were not tested to determine which pathogen was causing their sickness. Now, when these patients show up in hospitals, they are usually tested for the coronavirus, which could inadvertently reveal whether other respiratory diseases are on the rise.

“We may get more detail than we’ve had historically,” Moffitt said. “So the numbers alone will not tell the whole story.” Emergency room visits and hospitalizations, she said, will be more important to monitor than infections alone.

Ryan Cross can be reached at Follow him on Twitter @RLCscienceboss.