What Is Acute Bronchiolitis? Understanding Causes, Symptoms, and Treatment

Understanding Acute Bronchiolitis: A Common Respiratory Condition in Infants

Acute bronchiolitis is a respiratory illness characterized by inflammation of the bronchioles—the tiny air passages in the lungs with a diameter of less than 2 millimeters. This condition primarily affects infants and young children, especially those under the age of two. It ranks among the most frequent causes of hospitalization in this age group during the winter months.

Primary Cause: The Role of Viral Infections

The majority of acute bronchiolitis cases—approximately 80%—are triggered by the respiratory syncytial virus (RSV). RSV spreads easily through droplets in the air when an infected person coughs or sneezes. Other viruses, such as rhinovirus, parainfluenza, and human metapneumovirus, can also contribute to the development of this condition. Because infants have smaller airways and immature immune systems, they are particularly vulnerable to severe symptoms.

Recognizing the Symptoms: From Mild to Severe

The illness typically begins with mild upper respiratory tract symptoms resembling the common cold—runny nose, low-grade fever, and slight cough. Within two to three days, the infection progresses deeper into the lower respiratory tract, leading to more pronounced symptoms such as persistent coughing, wheezing, and difficulty breathing.

Signs of Severe Respiratory Distress

In more serious cases, infants may exhibit rapid breathing, with respiratory rates exceeding 60 breaths per minute. Heart rates can rise to around 180 beats per minute due to increased effort to oxygenate the body. Additional warning signs include nasal flaring, chest retractions (where the skin pulls in around the ribs with each breath), grunting, and cyanosis (a bluish tint to the skin caused by lack of oxygen). If left untreated, acute bronchiolitis can lead to respiratory failure, requiring urgent medical intervention.

Diagnosis and Management Strategies

Doctors typically diagnose bronchiolitis based on clinical presentation, physical examination, and patient history. In most cases, imaging or laboratory tests are not required unless complications are suspected. Treatment is largely supportive, focusing on hydration, maintaining oxygen levels, and clearing nasal congestion. Hospitalization may be necessary for infants showing signs of dehydration, hypoxia, or extreme fatigue from labored breathing.

Prevention and Long-Term Outlook

While there is no specific cure for viral bronchiolitis, preventive measures can significantly reduce risk. These include frequent handwashing, avoiding close contact with sick individuals, and ensuring clean feeding and sleeping environments. For high-risk infants, a monoclonal antibody called palivizumab may be administered seasonally to prevent severe RSV infection. Most children recover fully within one to two weeks, though some may experience recurrent wheezing in early childhood.

When to Seek Medical Help

Parents and caregivers should seek immediate medical attention if an infant shows signs of labored breathing, poor feeding, lethargy, or decreased urine output. Early recognition and appropriate care are crucial in preventing complications and ensuring a smooth recovery.