Atopic children are more susceptible to viral respiratory infection at the age of 2-5 years old

High burden of respiratory allergy in children warrants early identification and treatment with allergen immunotherapy

Respiratory allergy often begins in childhood and most commonly manifests as allergic rhinitis (upper airways) and/or asthma (lower airways). Children with upper respiratory allergy often suffer from coexisting asthma, and other comorbidities ranging from gastrointestinal disorders to emotional/mental health disorders. Consequently, the disease burden is considerable and profoundly impacts a child's daily life. Early identification and appropriate management are important to reduce disease burden, lower the risk of disease progression and additional comorbidities, and protect the child's future well-being. A window of opportunity for halting disease progression may open in the early stages of allergic disease and underlines the importance of early diagnosis and treatment of children at risk. This review offers advice on identifying children with a high disease burden who would benefit from early intervention. Allergen immunotherapy (AIT) modifies the cause of respiratory allergy and prevents disease progression. In clinical practice, AIT could be considered as an early treatment for eligible children, to achieve long-term symptom control and disease modification.

Bacteria and viruses and their role in the preschool wheeze to asthma transition

Wheezing is the cardinal symptom of asthma; its presence early in life, mostly caused by viral infections, is a major risk factor for the establishment of persistent or recurrent disease. Early-life wheezing and asthma exacerbations are triggered by common respiratory viruses, mainly rhinoviruses (RV), and to a lesser extent, respiratory syncytial virus, parainfluenza, human metapneumovirus, coronaviruses, adenoviruses, influenza, and bocavirus. The excess presence of bacteria, several of which are part of the microbiome, has also been identified in association with wheezing and acute asthma exacerbations, including haemophilus influenza, streptococcus pneumoniae, moraxella catarrhalis, mycoplasma pneumoniae, and chlamydophila pneumonia. While it is not clear when asthma starts, its characteristics develop over time. Airway remodeling already appears between the ages of 1 and 3 years of age even prior to the presence of atopic inflammation or an asthma diagnosis. The role of genetic defect or variations hampering the airway epithelium in response to environmental stimuli and severe disease morbidity are now considered as major determinants for early structural changes. Repeated viral infections can induce and perpetuate airway hyperresponsiveness. Allergic sensitization, that often precedes infection-induced wheezing, shifts inflammation toward type-2, while common respiratory infections themselves promote type-2 inflammation. Nevertheless, most children who wheeze with viral infections during infancy and during preschool years do not develop persistent asthma. Multiple factors, including illness severity, viral etiology, allergic sensitization, and the exposome, are associated with disease persistence. Here, we summarize current knowledge and developments in infection epidemiology of asthma in children, describing the known impact of each individual agent and mechanisms of transition from recurrent wheeze to asthma.