Viral infections in relation to age, atopy, and season of admission among children hospitalized for wheezing

Abstract

Background: Viral respiratory tract infections and atopy are associated with attacks of wheezing during childhood. However, information about the relationship between viral infections and atopy among children whose attacks of wheezing lead to hospitalization is unclear.

Objective: To evaluate the prevalence of viral respiratory tract pathogens among infants and children hospitalized for wheezing and to analyze the results in relation to the patient's age, atopic characteristics, and season of admission.

Methods: This was a case-control study of children (age 2 months to 18 years) admitted for wheezing to the University of Virginia Medical Center over a period of 12 months. Children without wheezing were enrolled as controls. Nasal secretions were evaluated for viral pathogens by using cultures, PCR tests, and antigen detection. Total IgE and specific IgE antibody to common aeroallergens was measured in serum.

Results: Seventy percent of children hospitalized for wheezing before age 3 years (n=79) were admitted between December and March, whereas 46% of children age 3 to 18 years (n=54) were hospitalized between September and November. Among children younger than 3 years, viral pathogens were detected in 84% (66/79) of wheezing children and 55% (42/77) of controls (P <.001). Respiratory syncytial virus was the dominant pathogen during the winter months, but rhinovirus was more common during other months. Total serum IgE levels were generally low, and values from wheezing and control subjects overlapped considerably. Among children 3 years and older, 61% (33/54) of subjects admitted for wheezing tested positive for virus (predominantly rhinovirus), compared with 21% (12/56) of controls (P <.001). The total serum IgE values among wheezing children (geometric mean, 386 IU/mL; 95% CI, 259-573) were substantially elevated compared with those of controls (geometric mean, 38 IU/mL; 95% CI, 26-56; P <.001). A significantly higher percentage of wheezing children compared with controls was sensitized to at least 1 of the inhaled allergens tested: 84% (36/43) compared with 33% (15/45; P <.001). The atopic characteristics of wheezing children who tested positive or negative for virus were similar.

Conclusions: 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.

Fig 1

A, Monthly admissions for wheezing for children <3 years old (open bars) and children age 3 to 18 years (black bars). B, Children age 3 to 18 years whose nasal secretions tested positive for virus, n = 33 (gray bars), or negative for virus, n = 21 (black bars).

Fig 2

Positive tests for virus with respect to age among wheezing patients. Color code indicates RSV (blue), rhinovirus (green), influenza A or B (red), and other viruses, ie, adenovirus, parainfluenza (1, 2, and 3), enterovirus, and coronavirus (yellow). The percentages of patients in each age group whose nasal secretions tested positive for ≥2 viruses are noted beneath the figure. For plotting the results, viruses that grew in culture were given preference and included 18 tests for RSV, 2 for influenza B, 2 for rhinovirus, and 1 for parainfluenza type 3.

Fig 3

Seasonal virus data for wheezing patients. Color code indicates RSV (blue), rhinovirus (green), influenza A or B (red), and other viruses, ie, adenovirus, parainfluenza (1, 2, and 3), enterovirus, and coronavirus (yellow ).

Fig 4

Percent of patients who tested positive for each virus. A, Wheezing and control children <3 years old. Sixty percent (33/55) of patients enrolled during the months of December through March tested positive for RSV. B, Wheezing and control children age 3 to 18 years.

Fig 5

Total serum IgE levels. Median and intraquartile ranges are indicated by solid lines within box plots. GM values are shown next to the boxes and are also indicated by dotted lines within the boxes.