Flu and cold season looks different because of the pandemic. Here are some tips to protect kids from viruses this winter.

Pandemic prevention practices such as masking and social distancing have upended expectations for the arrival of “sick season,” the traditional wave of colds, flu, and other respiratory illnesses that rise as temperatures fall, doctors at Children’s Hospital of Philadelphia said Wednesday.

CHOP, for example, saw an unusual springtime spike this year in cases of respiratory syncytial virus, known commonly as RSV, which in very young children can raise concerns about bronchitis and pneumonia. This was preceded by atypically low levels of RSV last fall and winter. Now RSV cases are increasing again, CHOP’s experts said, this time with more severe cases of the disease.

The hospital system believes an explanation lies in measures taken to limit the spread of coronavirus, said physician Ron Keren, CHOP’s chief medical officer.

“The last few years have been really unusual. It’s a product of the infection prevention practices in place,” Keren said.

Keren said many infants and young children born during the pandemic might not have had the chance to build up immunity to viruses such as RSV when public health policies kept people more socially isolated, which could be contributing to the more severe cases he and other doctors have been seeing this fall.

The higher volume of those cases is also contributing to crowding in hospitals. CHOP has been operating at or close to full capacity for the last several weeks, Keren said.

Parents can still take practical measures to help prevent seasonal illnesses in their kids, CHOP physicians said at a news conference pegged to the start of the cold-weather sick season. These include encouraging hand-washing, masking in large gatherings, and keeping kids home when they’re sick.

Parents can also supervise kids to make sure they learn good hand-washing practices, such as washing for a full 20 seconds and making sure to get soap between their fingers and on their wrists, said Katie Lockwood, an attending physician at CHOP.

As COVID mask and vaccination mandates have lifted, she noted that the changing rules may confuse parents and kids about how to best protect themselves from the virus.

“We know that things like ventilation and being outdoors can help prevent the spread. And we also have vaccines,” she said.

She said every family has to evaluate its own comfort levels around the continued risk of getting COVID-19.

“Some families and children may choose to continue masking whenever they’re out in public,” Lockwood said. “It’s important that we teach all of our children to respect other’s choices, whether they’re deciding to wear a mask or not.”

Lockwood recommended avoiding large gatherings or wearing masks during them — or holding events outside — to prevent transmission of illnesses during sick season.

But right now, COVID rates are flat or declining, and influenza rates are low as well, Keren said.

“We all have time to get our kids vaccinated, or boosted against both these viruses, before the numbers increase and it becomes harder to avoid an infection,” Keren said.

He noted that although children have a significantly lower risk of getting severe disease from COVID, some still become seriously ill, especially kids who are immunocompromised or who have other risk factors such as obesity.

Vaccines and the boosters can prevent those more severe cases, doctors noted.

CHOP’s experts also recommended that parents make sure their children are up to date on their vaccinations, especially ones they might have missed because of social distancing and isolation policies during the first waves of COVID.