How Respiratory Microflora Shapes RSV Severity and Long-Term Asthma Risks in Children

Respiratory microflora plays a key role in influencing the severity of respiratory infections, including childhood asthma and wheezing linked to respiratory syncytial virus (RSV), according to a study published in Pediatric Discovery.

RSV is the leading cause of lower respiratory tract infections in young children, particularly in those under 2-years-old, with severe cases often requiring hospitalization.

In addition to its health risks, RSV has been linked to the development of recurring wheezing and asthma.

Past studies suggest the respiratory tract’s microbial community, or microflora, plays a significant role in determining the severity of RSV infections and the development of these long-term conditions.

However, the impact of respiratory microflora on RSV infection remains foggy.

Based on the review of over 30 studies, researchers aimed to understand how different bacterial profiles — such as Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus — influence RSV outcomes in children under 18-years-old.

Reviewing databases such as PubMed, EMBASE, Web of Science, Cochrane Library, China Biology Medicine, CNKI and WanFang Data, researchers used a range of relevant MeSH terms, or keywords used to categorize medical and health-related articles, related to RSV and microbiota.

Additional searches were made through the WHO website, Google Scholar and preprint servers like BioRxiv and medRxiv.

Out of 33 studies, 19 focused on original research, with nasopharyngeal aspirates (NPA) being the most common sample source.

Findings revealed that after RSV infection, bacterial diversity in the respiratory tract decreased, with Haemophilus, Streptococcus and Neisseria emerging as dominant microbes.

The dominant microbial profiles varied by age, with Moraxella catarrhalis peaking around three months of age.

Streptococcus pneumoniae (S.pn) abundance displayed inconsistent effects on RSV severity, with some studies showing a negative correlation between S.pn density and disease severity, while others found a positive association.

Long-term outcomes indicated that microbial profiles, including Lactobacillus and Staphylococcus, may protect against recurrent wheezing, while Moraxella catarrhalis, Haemophilus, and S.pn were linked to an increased risk.

These findings add to the growing research connecting respiratory microflora with the severity of RSV infections and childhood asthma, which provides insights into how particular microbial profiles may affect long-term health.

It also offers support to factors that could influence RSV disease outcomes and introduces new methods such as transcriptomics to better understand the complex interactions between hosts and microbes.

Transcriptomics is the study of the transcriptome, which refers to the complete set of RNA molecules, including mRNA, rRNA and non-coding RNA, present in a cell or organism at a specific time.

Despite the study’s strengths, there are limitations including the use of conference abstracts, which can affect the reliability of the data, and the relatively small number of studies reviewed, making it difficult to draw broad conclusions.

In addition, the challenge of combining data across different studies may have impacted the accuracy of the findings.

Researchers suggest more diverse studies on this topic to understand the interactions between respiratory microflorae, host immune responses and RSV infection.

They also highlight the need for research in developing countries to address regional gaps, as well as how microflorae composition influences disease severity, recurrent wheezing and asthma.