RSV usually causes mild, cold-like symptoms, and is the most common cause of bronchitis and pneumonia in kids under the age of 1 in the U.S., according to the CDC.
The CDC also states that premature infants and young children with weakened immune systems, congenital heart or chronic lung disease are the most vulnerable to complications from RSV.
"Four out of every 1,000 babies under six months old are being hospitalized for RSV," said Dr. Ana Mann, a pediatrician with Christiana Care Pediatric Center.
A Wynnewood couple is doing everything they can to limit their six-week-old baby's exposure to RSV.
"We had several friends with babies that have unfortunately gone through it. We know from our pediatrician that it's very serious, especially in newborns and infants," said Mari Kalman of Wynnewood.
Like they did with COVID-19, they're avoiding crowded indoor spaces and opting to dine outdoors. RSV symptoms are similar to COVID and the flu in that it presents like a common cold.
RSV can cause severe respiratory inflammation and labored breathing in children under two.
"Babies, in general, are coming in with increased work of breathing, hypoxia, low oxygen levels, poor feeding, more irritability and those are all things we would look at when considering whether they need to be hospitalized or not," said Dr. Mann.
According to the Philadelphia Department of Health, there were about 500 cases last week, which is up from 450 cases the previous week.
Twenty-eight percent of RSV tests in the Philadelphia area are positive.
The unfortunate part for families is there is no treatment for this virus. Doctors say all you can do is clear out the child's nasal passages and keep the fever down.
There is a first-of-its-kind monoclonal antibody treatment that was just approved in Europe and is awaiting FDA approval in the U.S.
Even if it's approved, it won't be available until next year.