Bronchiolitis

Overview

Bronchiolitis is a common viral infection of the bronchioles, the smallest air passages in the lungs. It mainly affects infants and children under two years of age, with the highest impact in babies under six months. The infection causes the small airways to swell and fill with mucus, which makes it harder for air to move in and out and leads to coughing, wheezing, and rapid breathing.

Most cases are caused by respiratory syncytial virus (RSV), though other common respiratory viruses can be responsible. Bronchiolitis often starts like a regular cold and then moves into the chest over a few days. The great majority of children have a mild illness that improves with home care over one to two weeks. However, some babies, especially very young or premature infants, can become seriously ill and need hospital care, so it is important to know the warning signs.

Symptoms

Bronchiolitis usually begins with cold-like symptoms that then spread to the chest:

• Early symptoms: Runny nose, congestion, mild cough, and sometimes a low fever.
• As it progresses: A worsening cough, wheezing (a whistling sound when breathing out), and fast or labored breathing.
• Feeding difficulty: Babies may eat or drink less because breathing and feeding at the same time becomes hard.
• Signs of harder breathing: Flaring nostrils, pulling in of the skin around the ribs, and grunting.

Warning signs that a baby is becoming seriously unwell include very fast or difficult breathing, long pauses in breathing (apnea), bluish lips or skin, marked drowsiness, signs of dehydration, or far fewer wet diapers. These require urgent medical attention.

Causes

Bronchiolitis is caused by viruses that infect the small airways of the lungs. The most common cause is:

• Respiratory syncytial virus (RSV): Responsible for the majority of cases, especially in fall and winter.

Other respiratory viruses, including rhinovirus (the common cold virus), influenza, and others, can also cause bronchiolitis. These viruses spread easily from person to person through respiratory droplets when an infected person coughs or sneezes, and through contact with contaminated hands and surfaces. The infection inflames the bronchioles and fills them with mucus and shed cells, narrowing the airways and producing the typical cough and wheeze.

Risk Factors

• Age under 2 years, with the greatest risk in babies under 6 months
• Premature birth
• Underlying heart or lung conditions
• A weakened immune system
• Exposure to tobacco smoke
• Attending daycare or having older siblings who bring home infections
• Not being breastfed, which may offer some protection

Diagnosis

Bronchiolitis is usually diagnosed from the history and examination, and most children do not need tests:

• Clinical examination: Listening to the chest for wheezing and crackles and observing the child's breathing effort.
• Oxygen monitoring: A small sensor on the finger or toe to measure oxygen levels.
• Virus testing: A nasal swab may be used in some settings, such as the hospital, to identify RSV.
• Chest X-ray: Not routinely needed and reserved for unusual or severe cases.

Treatment

Because bronchiolitis is viral, antibiotics do not help, and treatment is mainly supportive:

• Home care: Keeping the baby comfortable, offering small, frequent feeds to maintain hydration, and using saline nose drops and gentle suction to clear a blocked nose.
• Fluids: Ensuring the child takes in enough liquid; watch for signs of dehydration.
• Fever and comfort: Appropriate fever-reducing medicine for age can help comfort.
• Hospital care: Some babies need extra oxygen, help with feeding through a tube or vein, and close monitoring; very ill infants may need breathing support.

Cough and cold medicines are not recommended for infants and young children. Most children recover at home within one to two weeks, although the cough can linger longer.

Prevention

• Wash hands often and keep the baby away from people with colds
• Avoid exposing infants to tobacco smoke
• Clean frequently touched surfaces and toys
• Keep young or high-risk babies away from crowded places during peak RSV season when possible
• Ask your doctor about RSV immunization options for eligible infants and during pregnancy
• Breastfeed when possible, as it may offer some protection

When to See a Doctor

Contact your doctor if your child has fast or labored breathing, is feeding poorly, or seems to be getting worse. Seek emergency care immediately if your baby:

• Is struggling to breathe, breathing very fast, or grunting with each breath
• Has pauses in breathing or turns blue or pale around the lips
• Is very drowsy, hard to wake, or unusually limp
• Shows signs of dehydration, such as very few wet diapers, dry mouth, or no tears

Very young and premature infants can worsen quickly, so it is best to seek advice early.

Related Topics

Frequently Asked Questions

References

1. American Academy of Pediatrics. Bronchiolitis.
2. Mayo Clinic. Bronchiolitis — Symptoms and causes.
3. Centers for Disease Control and Prevention (CDC). Respiratory Syncytial Virus (RSV).
4. MedlinePlus, U.S. National Library of Medicine. Bronchiolitis.