Pneumonia is more common in children younger than 5, and it can range from mild (like mycoplasma pneumonia, also known as "the walking pneumonia") to serious and potentially life-threatening.

While respiratory syncytial virus (RSV) may present like the common cold in many healthy children, it can be dangerous in babies and some young children.

The common cold is one of the most common illnesses among children—in fact, most children will have 8 to 10 colds by the time they’re two years old.