Re: RSV at 4??
I don't know about RSV-- not too familiar with it. But my DS is prone to lung problems-- bronchitis, turns into croupe, he'll get a cold, turns into a upper resp infectoni, bronchitis... croupe... get the picture? But it's never been RSV.
My friend's daughter, just turned 3, has RSV twice her fisrt year, once last winter. She's had a few bad colds and her asthma has been persistent-- where they are giong in (today) because they suspect RSV.