It's not just influenza that peaks in the winter. Almost every child gets respiratory syncytial virus by the age of two, however, some worse than others.
But why do some kids end up in the hospital?
At St. Mary's, the pediatric unit is packed.
Eight-week-old Sophia Kipling has had a very difficult few days. She won't remember them, but her mom will never forget what it was like to watch her struggle to breathe.
It all started when her older sister, 2-year-old Gracie, came home from daycare with a cold.
Sheri Kipling, Sophia's mom, says, "I did everything: disinfected the house, washed their toys, changed their beds, washed my hands religiously, and she still, she still got it."
Her pediatrician diagnosed Sohpia with respiratory syncytial virus, and within hours, she was in the emergency room.
"It can happen really fast, and what you think is just a cold, is something pretty serious in a small baby," Kipling responds.
It's true, most kids will get over RSV in few days, but it can be deadly for the very young preemies, those with congenital heart, or chronic lung conditions.
It starts out as normal cold and within three or four days, they start wheezing.
Pediatrician Dr. Lata Shukla says, "Once they start wheezing, then they have difficulty breathing, and their chest shows retractions and stuff. And they're losing oxygen supply, and they're turning blue."
Because their airways are so clogged, patients get nebulizer treatments while being kept in quarantine.
Adults can give the virus to children who easily pass it between them via nasal secretions that can stay alive for up to five hours on door handles and other surfaces.
Dr. Shukla explains, "If they're living in crowded conditions, like in daycare setting or if they have a lot of siblings. And again, if they're around smoke, that's a big factor too."
And now that Sophia's had RSV, she's more prone to getting it again or having other serious lung infections. So once she gets out of the hospital, her mom won't be sending her to daycare again anytime soon.
For premature babies and those with lung or heart conditions, doctors give them a monthly shot of synagis, the RSV vaccine. But it's not recommended for the entire infant population. It's an extremely expensive vaccine that's reserved for the very sick or vulnerable.