As the weather gets cooler and seasons shift to fall and winter, seasonal illnesses will likely hit your household. But the common cold and flu aren't the only illnesses parents should be concerned about. RSV is just as contagious and likely to be contracted by your little one (regardless of age). Learn the signs, symptoms, treatment, and ways to prevent RSV in this in-depth guide, medically reviewed by Dr. Kristina Javier, MD FAAP.