Pneumonia is a lung infection in which the air sacs (alveoli) get blocked with pus and other fluids, making it hard for the alveoli to transfer oxygen into the blood. Pneumonia is usually caused by a virus, but it can be caused by bacteria, or a combination of bacteria and viruses. Kids with chronic illnesses have weaker immune systems and are at greater risk for pneumonia.
Rapid, labored breathing, coughing, and a fever (101 degrees F. to 104 degrees F.) are telltale signs. Viral pneumonia comes on with a lower fever, less fatigue, and more wheezing, but viral and bacterial pneumonia have similar symptoms. A minor but persistent cough may also signal "walking pneumonia," a milder infection that doesn't leave you bedridden.
Keeping your child up to date with his vaccines will help prevent the infections that often lead to pneumonia. In particular, make sure he receives the pneumococcal conjugate vaccine (typically given at 2, 4, and 6 months, as well as between 12 and 15 months), which protects against seven strains of pneumonia-causing bacteria.
Half the time, pneumonia is viral, so you'd treat it as you would a cold. But your pediatrician may prescribe antibiotics just in case it's bacterial.
Call 911 if you spot more than one alarming symptom -- if your baby is lethargic, has trouble breathing, and has a fever (above 100.4 degrees F. for babies younger than 6 months; above 102 degrees F. for older kids), or has a bluish tint around the lips and nails.