RSV (Respiratory Syncytial Virus)
Chances your child will catch it: 90 percent of children are infected by age 2.
Symptoms: RSV causes common cold symptoms and in up to 40 percent of cases triggers bronchiolitis, an infection of the small airways, which leads to wheezing, rapid breathing, and a persistent cough.
Contagious? Yes, both during the incubation period (four to six days) and for three to eight days afterward.
Rx: Treat RSV as you would a cold. But call your doctor ASAP if your child has fast or labored breathing. He might need inhaled medication or, in severe cases, could require hospitalization.
You need to know: Air irritants make RSV symptoms worse, so avoid exposing your child to cigarette smoke, wood-burning fireplaces, and perfumes, says Ellen Schumann, MD, a pediatrician at Marshfield Clinic in Weston, Wisconsin.