Viral Etiology of Bronchopneumonia in Infants < 2 Years

Epidemiology of RSV

Approximately 90 % of children are infected with RSV by age 2, and up to 40 % develop a lower‑respiratory‑tract infection during the initial illness, indicating a very high early‑life burden of this virus 5.
In North America the incidence of RSV peaks between December and March, reflecting a clear seasonal pattern that clinicians should anticipate when evaluating infants with respiratory symptoms 5.

RSV is the most frequently detected viral pathogen in infants < 2 years, accounting for up to 40 % of identified pathogens and representing the leading cause of lower‑respiratory‑tract infections requiring hospitalization in this age group 1, 2, 3, 4.
The Pediatric Infectious Diseases Society and Infectious Diseases Society of America guidelines state that viral etiologies account for up to 80 % of community‑acquired pneumonia cases in children younger than 2 years 1, 2, 3.
Other viruses are detected less frequently, including adenovirus, bocavirus, human metapneumovirus, influenza A/B, parainfluenza viruses, coronaviruses, and rhinovirus 1, 2, 3.

Simultaneous infection with 2–33 % of hospitalized children with pneumonia involves two or more viruses, highlighting the commonality of viral co‑infection in this population 1, 2, 3.
Viral‑bacterial co‑infections are also frequent, making it difficult to attribute clinical severity to a single pathogen and underscoring the need for comprehensive diagnostic evaluation 1, 2, 3.

Although RSV predominates, bacterial pathogens—particularly Streptococcus pneumoniae—must be considered in the differential diagnosis and empiric treatment approach for bronchopneumonia in infants < 2 years old 1, 2, 3.