Acute Viral Bronchiolitis: A Complete Overview of Definition, Epidemiology, Pathophysiology, Symptoms, Treatment and Outcome

Abstract

Introduction:  Acute Viral Bronchiolitis (AVB) is a common viral respiratory infection in childhood, primarily affecting infants under 2 years of age. Predominantly caused by the Respiratory Syncytial Virus (RSV) in up to 90% of cases, AVB results in inflammation and obstruction of the smaller airways, manifesting as cough, wheezing, and respiratory difficulty. The disease is particularly dangerous for premature infants, children with congenital heart diseases, or immunodeficiencies, with up to 30% requiring hospitalization, significantly impacting healthcare systems and the quality of life of families. Method: An integrative literature review was conducted in June 2024 using databases such as PubMed/Medline and SciELO. The descriptors "bronchiolitis," "respiratory infection," "virus," and "infant" were combined with the boolean operators "AND" and "OR". Inclusion criteria involved research from 2004 to 2024 in English, Portuguese, and Spanish. Case reports, duplicate articles, or non-pertinent studies were excluded. Eighteen scientific articles and chapters from the "Tratado de Pediatria" by the Brazilian Society of Pediatrics (2017) were analyzed. Results: Bronchiolitis is defined as inflammation of the bronchioles, with guidelines varying between the American Academy of Pediatrics and European directives. It affects over one-third of children in their first two years of life, with up to 10% hospitalized. RSV is responsible for up to 75% of cases, followed by rhinovirus and other respiratory viruses. Bronchiolitis shows seasonality, with risk factors such as age under 6 weeks, prematurity, immunodeficiency, and congenital heart disease. It is characterized by inflammation, increased mucus production, necrosis, and airway edema. RSV, transmitted through inhalation of infected particles, causes epithelial necrosis and airway obstruction, leading to hyperinflation and atelectasis. Studies suggest an association between RSV infection and increased incidence of asthma in subsequent years. Initial symptoms include upper respiratory infection, progressing to respiratory difficulty, wheezing, tachycardia, and tachypnea. Severe cases require hospitalization. Differential diagnosis is essential, distinguishing from asthma, bacterial pneumonia, and other conditions. Treatment is predominantly supportive, with hydration and monitoring for warning signs. In 2013, the monoclonal antibody palivizumab was approved for prophylaxis in high-risk groups. Hypertonic saline nebulization showed efficacy in mild to moderate cases. The indiscriminate use of corticosteroids and bronchodilators is not recommended. Conclusion: AVB is a prevalent condition significant for pediatric hospitalizations, with RSV as the primary etiologic agent. Treatment is mainly supportive, with specific prophylaxis for high-risk groups. The review highlights the importance of appropriate clinical approaches and prevention for effective AVB management.