Surreal illustration of a child's lung intertwined with viruses and inflammatory cells, symbolizing the complex relationship between infection and asthma.

Unlocking the Mystery: Infections, Eosinophilia, and Childhood Asthma

Samir D’Costa monogram
Samir D’Costa in Health & Wellness October 2026 • 4 min read.

"A Deep Dive into the Intricate Relationship Between Early Infections, Immune Responses, and the Development of Asthma in Children"


Asthma's underlying mechanisms are complex and not entirely understood. One aspect is the interaction between infections, the immune system, and the onset of asthma in children. This article explores this connection, providing insights and practical knowledge.

For decades, researchers have investigated how respiratory pathogens contribute to asthma. However, critical questions remain unanswered. Which pathogens are most likely to trigger recurrent wheezing and asthma? Do these early infections directly cause asthma, or do they simply affect individuals who are already predisposed? What specific immunological processes are involved?

This article will explore the interactions between respiratory infections and asthma development, emphasizing the roles of specific pathogens and eosinophilia. Gain a deeper understanding of the underlying science, empowering you to make informed decisions about your child's health.

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Childhood Asthma in 2024

The US EPA reports that 6.5% of children had asthma in 2024. That year, 3.6% of children ages 0 to 17 had one or more asthma attacks in the past year. The EPA says the rate of asthma attacks increased in recent years following a decline since 2011, when it was 5.5%.

The Infection Link: How Early Infections Impact Asthma Development

Surreal illustration of a child's lung intertwined with viruses and inflammatory cells, symbolizing the complex relationship between infection and asthma.

It's well-documented that many infants hospitalized with bronchiolitis later develop asthma. Studies show that babies born during the winter virus season have a higher risk of developing asthma by age six. While the precise mechanisms are debated, it's clear that respiratory infections play a significant role in asthma development.

Respiratory syncytial virus (RSV) is often the main culprit. Most children contract RSV before age three, making it a major cause of bronchiolitis in infants. While no studies directly prove RSV causes asthma, research indicates a strong link between the timing of RSV infection and later asthma development.

  • RSV and Timing: Infants born just before peak RSV season face a heightened risk of developing asthma.
  • Preventive Measures: Giving high-risk children anti-RSV immune globulin can improve lung function and reduce asthma and allergy incidence.
  • The Big Picture: Since nearly all children contract RSV, other factors like genetics and environment also contribute to asthma's development.
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Research on Early Respiratory Exposures

A meta-analysis published in Frontiers in Medicine on February 16, 2026, evaluates the cumulative connection between preventive measures targeting early respiratory exposures and ongoing asthma-related consequences. The supplied description does not specify which preventive measures were examined or report effect estimates. A Nature topic page dated December 9, 2025, highlights research on viral infections and asthma development in childhood, but its supplied description gives no individual study findings.

Association Is Not Proof of Causation

Although data show a strong association between respiratory viral or bacterial infections and asthma, the review says further studies are needed to demonstrate causality clearly. Interpreting observational studies in young children is difficult because asthma symptoms can be hard to distinguish from respiratory tract infections (RTIs). RTIs are also the most frequent trigger of wheezing in early childhood, complicating interpretation of the association.

Eosinophil Prediction and Prophylaxis Findings

In a prospective study with an 18–20-year follow-up, elevated eosinophils during convalescence predicted increased asthma risk at ages 2–3 years (OR 2.26; 95% CI 1.29–3.95), 3–4 years (OR 2.24; 95% CI 1.27–3.95), and 8.5–10 years (OR 2.16; 95% CI 1.01–4.64), after adjustment for RSV etiology, age on admission, and earlier wheezing and atopy. By contrast, a six-year follow-up study of palivizumab prophylaxis in preterm infants found no significant difference in atopic asthma between treated and untreated groups: 15.3% versus 18.2% (P = 0.57). These studies report different outcomes: one assessed eosinophils as a predictor, while the other compared atopic asthma by treatment group.

Recent research highlights human rhinovirus (HRV) as another key player. While HRV is often found in asymptomatic children, it's a significant cause of wheezing illnesses. The severity of the illness can depend on individual factors or the specific virus strain. Studies show that HRV infections during the first three years of life can increase asthma risk tenfold. Other viruses, such as human bocavirus (HBoV) and human metapneumovirus (HMPV), have also been linked to wheezing and asthma.

The Path Forward: Focus on Early Intervention

Viral and bacterial infections significantly impact childhood respiratory health and can lead to long-term issues like recurrent wheezing. There's a strong link between early childhood infections and asthma, but the exact mechanisms are still unclear. A deeper understanding of these processes will enable clinicians to improve diagnosis, treatment, and monitoring of asthma. It's essential to shift focus from solely treating symptoms to addressing the root causes, ensuring the best possible care for young patients.

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Coordinated Care and New Approaches

A 2026 Frontiers in Pediatrics article identifies genetic predisposition, environmental exposures, and social determinants as factors influencing pediatric asthma outcomes. It emphasizes coordinated care involving caregivers, schools, and multidisciplinary healthcare teams. A Wiley review says advances in childhood asthma therapy are on the horizon, with studies exploring novel approaches to prevent asthma from starting or developing.

Clarifying Long-Term Causal Links

Early-life viral infection can affect the developing lung and immune systems, both of which are important in asthma development. Research has aimed for decades to establish whether these infections cause asthma later in childhood. A 2026 Frontiers editorial says important questions remain and calls for future longitudinal studies to clarify causal relationships among viral infections, epigenetic modifications, and asthma development.

Comparisons across age, atopy, and follow-up

Another comparison found that avoiding RSV infection during infancy was associated with a 26% lower risk of current asthma at age five than experiencing infant RSV infection. This risk comparison concerns RSV exposure and a defined childhood age, rather than odds across multiple infection types.[1]

The association between viral respiratory illness and persistent asthma or wheeze was stronger among atopic than nonatopic individuals, but the evidence for that difference was limited. The contrast suggests atopy may matter when interpreting infection-related associations, without establishing why the groups differ.[2]

A proposed immune pathway is that upper and lower respiratory infections may alter T-helper 2 and regulatory T-cell responses, potentially increasing asthma risk. This offers a possible biological link, not proof that the pathway explains the observed associations.[3]

What remains unresolved about infection and asthma

  • Do early infections cause asthma, and what pathophysiologic mechanisms would connect them? The association alone does not settle either question.[4]

Sources

  1. Respiratory syncytial virus infection during infancy and asthma during childhood in the USA (INSPIRE): a population-based, prospective birth cohort study. (pubmed.ncbi.nlm.nih.gov)
  2. The Association of Early Life Viral Respiratory Illness and Atopy on Asthma in Children: Systematic Review and Meta-Analysis. (pubmed.ncbi.nlm.nih.gov)
  3. Early-life respiratory tract infections and the risk of school-age lower lung function and asthma: a meta-analysis of 150 000 European children (pmc.ncbi.nlm.nih.gov)
  4. Infection, eosinophilia and childhood asthma (pmc.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

How are early childhood infections linked to the development of asthma?

The connection between early infections and asthma development in children is complex. Respiratory infections, especially those occurring in early childhood, are believed to play a significant role in the development of asthma. Specific pathogens like Respiratory Syncytial Virus (RSV) and human rhinovirus (HRV) have been identified as key players. However, the precise mechanisms through which these infections contribute to asthma are still not completely understood. Further research is needed to fully understand the nature and factors related to childhood asthma.

2

What is Respiratory Syncytial Virus (RSV), and how does it relate to asthma in children?

Respiratory Syncytial Virus (RSV) is a common virus that affects most children before the age of three. It is a major cause of bronchiolitis in infants, which is the inflammation of the small airways in the lungs. Research suggests a strong link between the timing of RSV infection and later asthma development. Infants born just before peak RSV season appear to face a heightened risk of developing asthma. Giving anti-RSV immune globulin to high-risk children can improve lung function and reduce asthma and allergy incidence. However, other factors also play a role.

3

What role does human rhinovirus (HRV) play in childhood asthma?

Human rhinovirus (HRV) is another key virus that has been identified as an important contributor to childhood asthma. While HRV is often found in asymptomatic children, it is also a significant cause of wheezing illnesses. Studies have shown that HRV infections during the first three years of life can increase the risk of developing asthma tenfold. The severity of the illness caused by HRV can vary depending on individual factors or the specific virus strain involved.

4

What is the role of Eosinophilia in the context of asthma and infections?

Eosinophilia is not specifically explained. It usually refers to a higher than normal level of eosinophils in the blood. Eosinophils are a type of white blood cell that is part of the immune system. They are often associated with allergic reactions and parasitic infections. In the context of asthma and infections, eosinophilia may indicate an immune response to certain pathogens or allergens that could be contributing to the development or exacerbation of asthma symptoms. Further studies are needed to confirm the role.

5

Why is early intervention important in addressing childhood respiratory infections and asthma?

Early intervention is important because viral and bacterial infections can significantly impact childhood respiratory health and lead to long-term issues such as recurrent wheezing and asthma. Shifting focus from solely treating symptoms to addressing the root causes of these issues is essential for providing the best possible care for young patients. A deeper understanding of the processes involved in early childhood infections and asthma development will enable clinicians to improve diagnosis, treatment, and monitoring of asthma.

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