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Early-life lung and gut microbiota and RSV infection: What is the connection?

Respiratory syncytial virus (RSV) infection has been considered as the most prominent cause of bronchiolitis till six months of age. Although prematurity is an independent risk factor for bronchiolitis, but the severity of the disease varies in different individuals, proposing that there may be some other factors (extrinsic or intrinsic), that contribute to differential response to same viral infection and severe RSV disease in some individuals.

Respiratory Syncytial Virus (RSV) infects 30%-60% of infants and almost all children by 2 years of age

The perturbations in the microbiota establishment in children impacts the long-term microbiota composition, which eventually leads to predisposition to diseases during childhood and later in life.

Early-life respiratory microbiota: Key to respiratory health

  • Respiratory microbiota differs in healthy vs patients with health and disease conditions.
  • Respiratory tract infection in children presents reduction of Corynebacterium and Dolosigranulum, enrichment of Moraxella very early in life, followed by later enrichment of Neisseria and Prevotella species.
  • Nasopharyngeal microbiome dominated by Haemophilus influenzae and Streptococcus is responsible for hospitalization and severe RSV infection in children.
  • Respiratory microbiome have high presence of Haemophilus, Moraxella or Streptococcus, and Klebsiella in infants hospitalized for severe RSV bronchiolitis and later who developed recurrent wheezing.

Early-life gut microbiota: Implications for health outcomes

  • Gut microbiome influences lung immunity and contributes to long-term effects on health and disease.
  • Microbiome communities in bottle-fed infants correlate to the development of allergic diseases later in life.
  • Gut bacteria dysbiosis during infancy increases the risk of asthma later in life.
  • Considering the hypothesis of the gut-lung axis, gut dysbiosis affects disease severity in RSV infection.
  • Significant enrichment of Clostridiales, Odoribacteraceae, Lactobacillaceae, and Actinomyces is determined in moderate and severe RSV-positive infants in comparison to healthy group.
  • Infants with Bacteroides-dominant profile have a high probability for bronchiolitis.

Alteration of gut and lung microbiota leads to the advent of probiotics that shape the development and activation of healthy immune system in children.


  1. Yagi K, Asai N, Huffnagle GB, et al. Early-life lung and gut microbiota development and respiratory syncytial virus infection. Front Immunol. 2022;13:877771. Available at:
MAT-IN-2201306 V1.0 06/22