With mask wearing and social distancing in effect throughout the fall and winter as COVID-19 cases surged, the flu season — which generally peaks between December and February — was nearly nonexistent this past year.

As COVID-19 cases in Connecticut have plummeted and people resume more normal activities, local doctors say they've seen a slight uptick in cases of the common cold. Influenza isn't circulating now, and a variety of variables — in virology and human behavior — make it difficult to predict what will happen next flu season.

Gov. Ned Lamont's office reported Friday the statewide COVID-19 test positivity rate was 0.44% and 36 people were hospitalized. By comparison, hospitalizations surpassed 1,200 in December and the positivity rate climbed above 10% in January.

"Because people are not masking anymore, we're certainly seeing the normal, run-of-the-mill respiratory diseases rising again," Dr. Ulysses Wu, system director for infectious diseases at Hartford HealthCare, said Thursday.

He cited rhinovirus, adenovirus, human metapneumovirus, and coronaviruses that have been circulating since long before the COVID-19 pandemic — which all cause the common cold. But he noted Hartford HealthCare is "not seeing large amounts of common cold," and it's not the type of thing that is sending people to the hospital.

Wu and Dr. Oliver Mayorga, chief medical officer at Lawrence + Memorial Hospital in New London, both said the increase coincides with the removal of mask mandates and a lack of social distancing.

Mayorga said L+M has not seen a rush of hospitalizations due to non-COVID illnesses, though he noted Yale New Haven Children's Hospital has seen a bump in bronchiolitis, a lung infection in children that usually circulates in the winter.

But how do doctors know they're seeing more respiratory viruses rather than seasonal allergies?

Mayorga said there is a close correlation between allergy symptoms and pollen counts, whereas that's not the case with respiratory conditions and pollen counts. He also noted that respiratory illnesses often involve a deep cough and bringing up phlegm, not the case with allergies.

East Lyme pediatrician Dr. Fred Santoro said there's been a bit of an increase in rhinovirus in the area, and an increase in other parts of the state in respiratory syncytial virus, a virus spread through droplets and contact with contaminated surfaces.

On June 10, the CDC issued a health advisory about increased RSV activity across the South, and encouraged broader testing for RSV among patients with respiratory illness who test negative for the coronavirus.

RSV is the most common cause of bronchiolitis, according to the CDC. On average, it leads to 58,000 hospitalizations annually among children under 5 and 177,000 hospitalizations among adults over 65.

The CDC said that in April 2020, "RSV activity decreased rapidly, likely due to the adoption of public health measures to reduce the spread of COVID-19," but the agency observed an increase of RSV reports since late March. The CDC said since older infants and toddlers didn't have typical exposure levels during the past 15 months, they might now be at increased risk of severe RSV-associated illness.

What about next flu season?

By mid-April of 2020, the Connecticut Department of Public Health had reported 3,013 influenza-associated hospitalizations for the 2019-2020 flu season. By the same time this year, DPH had reported just 13 hospitalizations.

What the next flu season looks like will depend on the particular strain circulating, influenza vaccination rates, and masking, social distancing and hand washing.

"Covid mitigation strategies of wearing masks, hand hygiene, social distancing and limiting gatherings were effective in limiting transmission of both the cold and flu viruses," said Mary Day, public health nurse at Ledge Light Health District.

Wu said people need to wash their hands and also not expose others to illness if they're sick, saying, "That's one of the biggest things that still happens, people come to work sick, they go to parties sick."

Mayorga also said the severity of a given flu season depends on the virulence, or contagiousness, of the dominant influenza strain that year.

Another factor is how many people get the flu vaccine, and his hope is that the public understanding of the coronavirus means more people get the influenza vaccine than before the pandemic.

According to CDC data, the median effectiveness rate for the flu vaccine over the past 10 years is about 42%, but it was as low as 19% in the 2014-15 flu season.

Alan Siniscalchi, surveillance coordinator for influenza, bioterrorism and public health preparedness at DPH, said in an email that the department — along with the CDC and World Health Organization — is "closely watching flu and other respiratory virus activity in countries within the southern hemisphere (who are entering their winter) for early signs of what may be coming our way, although it is too early to accurately predict the severity of our next cold and flu season."

What's happening at childcare centers?

Childcare providers are in an interesting position. Unlike adults, children under age 12 can't get the COVID-19 vaccine, but unlike many places, childcare centers still require all children over 3 and all staff — regardless of vaccination status — to wear a wear a mask indoors. That's according to guidance from the Connecticut Office of Early Childhood.

Patty Testa, owner of Child's Play in Ledyard, said she's seeing more allergy-type symptoms and head colds than she normally sees this time of year, but the center hasn't had any outbreaks of hand, foot and mouth disease or RSV — and no COVID-19.

She said Child's Play is still doing temperature checks at the door and heavy-duty sanitizing, and that "hand washing is a constant story." As COVID-19 numbers go down, Testa would like to see masks go away soon, but she likes the temperature checks and plans to stick with them.

Deborah Monahan, executive director of Thames Valley Council for Community Action, said TVCCA has not seen any activity they're concerned about. TVCCA runs Little Learners and Head Start programs across the region.

She thinks everyone has learned a lot from the pandemic.

"I think we respect colds and flus a little bit more than we did a year ago, and being mindful, I think, of each other," Monahan said. "I've said this all along to staff: 'If you're sick, don't come to work.' I think we mean it now more than ever."

e.moser@theday.com