PHILADELPHIA (WPVI) --A host of viruses go around every winter, but RSV is one that causes a lot of concern for the parents of very young children.
Coughing, sneezing and kids blowing noses, it's the sound of winter.
But the culprit behind it could be RSV - respiratory syncytial virus.
It's the most common cause of cold symptoms in young children.
Dr. Eileen Everly of Children's Hospital of Philadelphia says, "Almost everyone has had this virus at one point in their life. Most kids have had it by the age of 2."
Dr. Everly says most of the time, it's not a major concern.
"In kids with normal immune systems, it's an ugly cold- 7 to 10 days - they get over it," said Dr. Everly.
But for some babies - like those born premature, with suppressed immune systems, underdeveloped lungs, or lung diseases, RSV can lead to more serious problems.
They may need hospital care, including oxygen or a ventilator.
Dr. Everly says RSV can get bad quickly, so parents need to be alert for the signs.
Such as a young child reluctant to feed, drink or play.
"If they're breathing fast all the time, that's bad," said Dr. Everly
She also says, "If the nostrils are flaring, that's a huge concern."
For those symptoms, get medical help right away.
RSV is very contagious. It spreads through coughs or sneezes, and can live on surfaces, as well as hands and clothing.
It's important to clean those surfaces often, since older kids can bring it home to younger ones.
And everyone should wash their hands often, especially after contact with someone who has a cold.
Philadelphia's peak RSV season is November through March, but it varies elsewhere in the U-S.
And in Florida, the peak begins in July.
So parents should know the signs and always be vigilant.