Bronchiolitis is an infection that affects the lower respiratory tract of infants and young children under 24 months of age.
Bronchiolitis typically affects children younger than 24 months of age and is most common among infants younger than 6 months. During the first year of life, bronchiolitis affects about 11 of every 100 children. However, during some epidemics, a much higher proportion of infants are affected. Most cases occur between November and April, with a peak incidence during January and February.
Bronchiolitis is most often caused by
However, other viruses, such as influenza, other forms of parainfluenza, metapneumovirus, and adenoviruses, are sometimes involved. Rare causes include rhinoviruses, enteroviruses, measles virus, and the bacteria Mycoplasma.
Infection with any of these viruses can cause inflammation of the airways. The inflammation causes the airways to narrow, obstructing the flow of air into and out of the lungs. In severe cases, children have a low level of oxygen in their bloodstream.
The infection may be more common or more severe among infants whose mothers smoke cigarettes, particularly those who smoked during pregnancy. The infection seems to be less common among breastfed infants. Parents and older siblings can be infected with the same virus, but for them the virus usually causes only a mild cold.
Bronchiolitis starts with symptoms of a cold—runny nose, sneezing, mild fever, and some coughing. After several days, children develop difficulty breathing, with rapid breathing and a worsening cough. Usually children make a high-pitched sound when breathing out (wheezing—see Wheezing in Infants and Young Children). In most infants, the symptoms are mild. Even though infants may breathe somewhat rapidly and be very congested, they are alert, happy, and eating well.
More severely affected infants breathe rapidly and shallowly, use a lot of their respiratory muscles to breathe, and have flaring of their nostrils. They seem fussy and anxious and can become dehydrated because of vomiting and difficulty with drinking. A fever usually is present but not always. Some children also develop an ear infection. Premature infants or infants younger than 2 months sometimes stop breathing temporarily. In very severe and unusual cases, the child may become blue around the mouth because of a lack of oxygen.
A doctor bases the diagnosis on the symptoms and the physical examination. Doctors measure oxygen levels in the blood by placing a sensor on a finger (pulse oximetry).
Sometimes the doctor swabs mucus from deep inside the nose to try to identify the virus in the laboratory. Other laboratory tests may be done, and sometimes a chest x-ray is needed.
Most children recover at home in 3 to 5 days. With proper care, the chance of developing serious consequences due to bronchiolitis is low, even for children who need to be hospitalized.
Some children have repeated episodes of wheezing after having had bronchiolitis.
Most children can be treated at home with fluids and comfort measures.
During the illness, frequent small feedings of clear fluids may be given. Wheezing and coughing may continue for 2 to 4 weeks. Increasing difficulty in breathing, bluish skin discoloration, fatigue, and dehydration indicate that the child should be hospitalized. Children who have congenital heart disease or lung disease or an impaired immune system may be hospitalized sooner and are far more likely to become quite ill from bronchiolitis.
In the hospital, oxygen levels are monitored with a sensor attached to a finger or toe, and oxygen is given by an oxygen tent or face mask. Rarely, a ventilator may be needed to assist breathing.
Fluids are given by vein if the child cannot drink adequately.
Inhaled drugs that open the airways (bronchodilators) and corticosteroids (to suppress inflammation) may be tried, but their effectiveness in treating bronchiolitis is questionable.
Doctors no longer use the antiviral drug ribavirin (given by nebulizer) except for children whose immune system is extremely weak. Antibiotics are not helpful unless the child also has a bacterial infection.
Children who are at high risk of serious complications, such as those who have severe congenital heart disease or who were born very prematurely, may be given palivizumab to help prevent RSV infection. Palivizumab is an antibody to RSV.
Last full review/revision December 2014 by John T. McBride, MD