Bronchiolitis is a common respiratory illness in childhood.  It results from infection of the lungs with viruses that cause respiratory symptoms such as congestion, cough, and wheezing.  RSV (Respiratory Syncytial Virus) infection is the most common cause of bronchiolitis. The Human metapneumovirus, adenovirus, rhinovirus and para-influenza virus are other viruses that can cause bronchiolitis.  All these viruses cause common cold symptoms.  Children who catch these infections most often have what amounts to a deep “chest cold”.  Most of the respiratory viruses that cause cause bronchiolitis, such as RSV,  are not serious and resolve without incident in about two weeks. Please see our common cold page for treatment advice.

RSV Infections

Because RSV is by far the most common cause of bronchiolitis, we will turn our attention to describing this infection.  Both adults and children can catch RSV infections.  Most children in the United States will become infected with RSV by their second birthday.  Each year, usually in the winter months, we have epidemics of RSV infections. In the US, there are usually about 3 million children who will get RSV infections annually. Because RSV infections do not cause life long immunity, you can catch RSV many times. The infection is very contagious. The usual story we get from patients is that “the whole house is sick” with a bad chest cold. The problem that RSV infection presents is that very young children less than 12 months old, children with medical problems such as prematurity and heart disease, and children with asthma who catch RSV can develop more severe breathing problems than just common cold symptoms with the development of breathing difficulty. This breathing difficulty is similar to what children with asthma experience during an asthma attack:  wheezing and shortness of breath. Approximately 20% of children less than two years of age will develop wheezing with breathing difficulty when they are infected with RSV. In very rare cases, the breathing difficulty of RSV bronchiolitis can even progress to respiratory failure requiring hospitalization. Thankfully, this condition is rare.

To lessen the burden of severe RSV infection in premature infants and infants with chronic medical conditions such as lung problems, heart problems, depressed immune systems and other conditions, we now have a preventative treatment to help prevent severe disease due to RSV.  Synagis is a prescription injection that provides  infection-fighting antibodies that these babies lack, helping protect their vulnerable lungs from RSV.  If your baby has one of these risk factors, contact us about Synagis.

Symptoms of Bronchiolitis

For the 20% of children who catch RSV and then develop bronchiolitis, the symptoms have to do with inflammation of the smallest air passages of the lungs, the bronchioles. Just as a cold virus can make the nose become congested and filled with mucous, RSV infection in some children can “go down into the chest” and cause the bronchioles to become swollen, constricted, and filled with thick mucous. These factors cause the lungs to become stiff with obstruction to air flow which is especially seen when the child tries to exhale. The obstruction to airflow in the lungs causes the hallmark symptom of bronchiolitis, wheezing. Wheezing refers to the high pitched, or whistling sound that air makes when being forcibly pushed through swollen, constricted air passages.

In addition to wheezing, the swollen, constricted, mucous filled bronchioles cause a severe, wet sounding cough as the child tries to clear the thick mucous from the airways. Coughing is an important defense mechanism of the body in bronchiolitis which should not be interfered with because it protects against the development of bacterial pneumonia. Another symptom of bronchiolitis is rapid breathing. This is usually mild when the respiratory rate is 40 to 60 breaths taken every 60 seconds. Respiratory rates greater than 60 breaths per 60 seconds while the child is not active are more worrisome. This may indicate that the child is having difficulty getting enough air in and out of the lungs to meet the demands of the body. Often this type of respiratory distress is accompanied by retractions, which refers to sinking in of the skin between the ribs, near the collar bone and at the base of the neck which occurs with breathing. Another sign of a more serious problem with breathing is audible wheezing as the child exhales. Sometimes, with more severe distress, the child’s breathing can actually become quieter indicating less air movement. Rapid respirations above 60 breaths per minute accompanied by retractions and labored breathing in a child whose respirations are very quiet are not normal and are worrisome. You should seek immediate medical attention in such circumstances.

Usual Course of Bronchiolitis

RSV bronchiolitis is usually a 14 day illness which like other viruses has a typical clinical course. After an incubation period of 4 to 7 days, the first symptom of RSV is a runny nose which is usually associated with fever. The runny nose is typically very bad with copious clear mucous running out of the nose. A cough then develops one to two days later, which is soon followed by wheezing and sometimes shortness of breath. Very young infants less than 6 months old who catch RSV are particularly prone to severe disease and apnea (stopping breathing).

The following graph shows the expected time course and symptoms of RSV.

  • Runny Nose                    X   X   X   X   X   X   X   X    x    x
  • Fever                                      X   X   X   X   X   X
  • Cough                                                 X   X   X   X   X   X    X    X    x    x
  • Wheezing                                                 X   X   X   X   X    X    x    x
  • Apnea                                                             X   X   X
  • Hospitalization                                            X   X   X   X   X   X   X
  • Contagious               X   X   X   X   X   X   X   X   X   X    X    x   x    x
  • Days of illness          0   1    2    3   4    5    6    7   8    9   10  11  12  13  14

As seen by the graph above, RSV takes several days to develop. The course of RSV is predictable, it gets worse for several days then gradually gets better. Like other viral  infections, it is impossible to effectively treat bronchiolitis to prevent severe disease. The disease is going to run its course despite our best efforts. Therefore, even if parents seek prompt medical attention at the beginning of an RSV illness with the initiation of appropriate treatment, the child may worsen despite that treatment, and require hospitalization. Of the 3 million children who contract RSV each year in the US about 2% will require hospitalization.  In addition, the cough associated with bronchiolitis may last up to 6 to 8 weeks.


The treatment of RSV depends on the severity of the illness. Children who have only nasal congestion and cough without breathing difficulty require only “common cold” treatment as described in this handbook (please refer to this). Again, 80% of children who catch RSV will fall into this category.

Children who have mild wheezing should be seen in the office for an appointment during regular office hours. In years past, it was usual practice to treat children with wheezing with an inhaled asthma medication called albuterol.  This medication is a derivative of adrenaline which opens the lungs by helping to relax the airways which are constricted. For many years, this medication was a mainstay in the treatment of bronchiolitis.  In recent years however, multiple studies have shown that albuterol really doesn’t improve this disease.  Children with RSV infection will usually get over bronchiolitis on their own without treatment.  Therefore, the American Academy of pediatrics has issued a practice guideline which states that children with bronchiolitis do not need inhaled albuterol, chest x-rays nor RSV tests.  Watchful waiting is all that is needed.  The AAP does recommend that children with bronchiolitis have oxygen saturation testing (pulse ox) to insure that supplemental oxygen is not needed.

Other things you can do at home include:

  • Give plenty of fluids.  Watch for sign of dehydration.
  • Use a humidifier. Humidity helps to loosen thick secretions so that they can be coughed up.
  • Do not smoke around your child with bronchiolitis. This is extremely harmful and may well cause your child to develop respiratory failure.
  • In young children, suction the nose to remove mucous. You should use saline drops with this. Please see the section on “common cold” on how to do this.  Antibiotics do not help RSV infection because it is a viral illness and antibiotics do not treat viruses. Ear infections are common with RSV occurring in 20 to 30 % of the cases. You should know however, that the antibiotics while helping the ear infection will do nothing for the RSV infection.

Contact us within 24 hours if the following occur:

  • Your child does not take enough fluids in and begins to show early signs of dehydration (see the Parents Medical Handbook for a description of the signs of dehydration).
  • Your child develops an earache.
  • Your child develops difficulty sleeping, but is OK otherwise.
  • More severe breathing problems are much more worrisome. You should contact us immediately if:
  • Your child develops labored or difficult breathing.
  • Your child develops rapid breathing faster than 60 breaths per 60 seconds while your child is quiet.
  • Your child develops significant retractions (sinking in of the skin between the ribs, near the collar bone and at the base of the neck which occurs with breathing)
  • Your child’s wheezing worsens.
  • Your child stops breathing or passes out.
  • Your child appears to be sicker and not doing well.
  • Your child develops a blue color of the lips and the area around the lips.

Other information: Your child is contagious for two weeks from the beginning of the illness. Usually the illness is thought to be noncontagious when the wheezing disappears. The illness is spread by direct contact with infected nasal secretions. Therefore, avoidance of infected nasal secretions is important. Hand-washing is an effective tool at preventing the spread of RSV as is avoiding being around someone with RSV.

Reviewed by Dr. Byrum 12/11/2021