Viral infections were the dominant risk factor for wheezing among children hospitalized before 3 years of age. By comparison, a large majority of the wheezing children age 3 to 18 years had striking atopic characteristics that may be critical as a risk factor for hospitalization and an adverse response to viral infections, especially infections caused by rhinovirus.

Background The relevance of allergic sensitization, judged by titers of serum IgE antibodies, to the risk of an asthma exacerbation caused by rhinovirus is unclear. Objective To examine the prevalence of rhinovirus infections in relation to the atopic status of children treated for wheezing in Costa Rica, a country with an increased asthma burden. Methods The children enrolled (n=287) were 7 through 12 years old. They included 96 with acute wheezing, 65 with stable asthma, and 126 non-asthmatic controls. PCR methods, including gene sequencing to identify rhinovirus strains, were used to identify viral pathogens in nasal washes. Results were examined in relation to wheezing, total IgE, allergen-specific IgE antibody, and levels of expired nitric oxide (FENO). Results Sixty-four percent of wheezing children compared to 13% of children with stable asthma and 17% of the non-asthmatic controls tested positive for rhinovirus (p<0.001 for both comparisons). Among wheezing subjects, 75% of the rhinoviruses detected were Group C strains. High titers of IgE antibodies to dust mite allergen (especially Dermatophagoides sp) were common and correlated significantly with levels of total IgE and FENO. The greatest risk for wheezing was observed among children with titers of IgE antibodies to dust mite ≥17.5 IU/ml who tested positive for rhinovirus (odds ratio for wheezing: 31.5; 95% CI 8.3–108, p<0.001). Conclusions High titers of IgE antibody to dust mite allergen were common and significantly increased the risk for acute wheezing provoked by rhinovirus among asthmatic children.

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Rationale: Most virus-induced attacks of asthma are caused by rhinoviruses (RVs).Objectives: To determine whether people with asthma are susceptible to an increased viral load during RV infection.Methods: Seventy-four children (4-18 yr old) were enrolled; 28 with wheezing, 32 with acute rhinitis, and 14 without respiratory tract symptoms. Nasal washes were evaluated using quantitative polymerase chain reaction for RV to judge viral load along with gene sequencing to identify strains of RV. Soluble intercellular adhesion molecule-1, IFN-l 1 , and eosinophil cationic protein in nasal washes, along with blood eosinophil counts and total and allergen-specific IgE in sera, were also evaluated. Similar assessments were done in 24 young adults (16 with asthma, 8 without) who participated in an experimental challenge with RV (serotype 16).Measurements and Main Results: Fifty-seven percent of wheezing children and 56% with acute rhinitis had nasal washes testing positive for RV. The geometric mean of viral loads by quantitative polymerase chain reaction in washes from wheezing children was 2.8-fold lower, but did not differ significantly from children with rhinitis (7,718 and 21,612 copies of viral RNA per microliter nasal wash, respectively; P = 0.48). The odds for wheezing were increased if children who tested positive for RV were sensitized to one or more allergens (odds ratio, 3.9; P = 0.02). Similarly, neither peak nor cumulative viral loads differed significantly in washes from adults with asthma compared with those without asthma during the experimental RV challenge.Conclusions: During acute symptoms, children infected with RV enrolled for wheezing or acute rhinitis had similar viral loads in their nasal washes, as did adults with and without asthma infected with RV-16 experimentally.