Infectious pathogens and bronchiolitis outcomes

Abstract

Bronchiolitis is a common early childhood illness and an important cause of morbidity, it is the number one cause of hospitalization among US infants. Bronchiolitis is also an active area of research, and recent studies have advanced our understanding of this illness. Although it has long been the conventional wisdom that the infectious etiology of bronchiolitis does not affect outcomes, a growing number of studies have linked specific pathogens of bronchiolitis (e.g., rhinovirus) to short- and long-term outcomes, such as future risk of developing asthma. The authors review the advent of molecular diagnostic techniques that have demonstrated diverse pathogens in bronchiolitis, and they review recent studies on the complex link between infectious pathogens of bronchiolitis and the development of childhood asthma.

Keywords::

• acute respiratory infection
• asthma
• atopy
• bronchiolitis
• IgE
• recurrent wheeze
• respiratory syncytial virus
• rhinovirus

Disclaimer

The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Allergy and Infectious Diseases or the National Institutes of Health.

Financial & competing interests disclosure

Camargo CA was supported by grant U01 AI-67693 from the National Institutes of Health (Bethesda, MD, USA). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• The effects of specific infectious pathogens on the short- and long-term outcomes of a child with bronchiolitis are not fully understood, but differences are generally assumed to be inconsequential. Accordingly, the 2006 American Academy of Pediatrics clinical practice guidelines for bronchiolitis recommended limiting viral testing for children with bronchiolitis.

• However, a growing number of studies of bronchiolitis have linked specific pathogens to important clinical outcomes such as recurrent wheezing and childhood asthma.

• Bronchiolitis with respiratory syncytial virus (RSV)/rhinovirus (RV) coinfections may not have a higher severity of illness but rather a protracted clinical course (e.g., longer hospital length of stay and higher chance of relapse). As RVs have been linked to nosocomial infections, these studies challenge the conventional cohorting efforts that rely on RSV and influenza virus testing alone.

• RSV bronchiolitis may lead to a recurrent wheeze and asthma (odds ratio [OR]: 3.8); however, this association weakened over time and was no longer significant by the age of 13 years.

• Recent cohort studies have linked RV lower respiratory tract infection in early childhood to higher risk of recurrent respiratory symptoms and abnormal lung function and much higher risk of developing recurrent wheezing (OR: 10) and childhood asthma (OR: 26).

• A few small cohort studies report that children with atopy and viral respiratory illness (not necessarily bronchiolitis) at the age of 1 year or older are at particularly high risk of developing childhood asthma.

• Nevertheless, causal inferences about the association between viral bronchiolitis and asthma are premature. RV infections may be directly involved in development of asthma through promoting airway inflammation and remodeling. Alternatively RV infections may also represent a proxy for children predisposed to repetitive RV infection and asthma. Furthermore, these two explanations are not mutually exclusive.