Sneezing and wheezing: Viruses and bacteria in early childhood wheezy episodes

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Science Translational Medicine  01 Jul 2015:
Vol. 7, Issue 294, pp. 294ec111
DOI: 10.1126/scitranslmed.aac8106

Viruses that infect the respiratory tract are known to trigger wheezing in young children; whether bacteria also trigger wheezing is not so clear. To investigate how specific pathogens affect wheezy illness, Carolsson and colleagues assessed viruses and bacteria collected from the airways of young children during wheezing episodes. The children—from the COPSAC2000 cohort—were followed with daily diary cards and doctor visits during wheezy episodes. The authors gathered a total of 515 nasopharynx and hypopharynx aspirates from 216 children during acute wheezing incidents (483 were tested for virus detection by PCR, 420 for bacteria by microbial culture, and 388 for both bacteria and virus).

Similar to others’ reports, viruses were detected in 65% (350 of 530) of the pharyngeal aspirates—with picornaviruses (85% were rhinovirus), respiratory syncytial viruses (RSV), and coronviruses being the most prevalent viral agents. The authors also discovered bacteria in 85% (412 of 483) of the pharyngeal samples that they cultured. Streptococcus pneumonia, Haemophilus influenza, and Moraxella catarrhalis were the most commonly found bacteria. Of the samples tested for both viruses and bacteria, 55% were coinfected. These findings suggest that, in addition to viruses, common respiratory bacteria are associated with acute wheezing episodes, possibly causing exacerbations.

The incidence of RSV peaked in the winter months, whereas the viral and bacterial isolates did not show seasonal variation. The average duration of illness was 9 days, a value that, surprisingly, was independent of the identity of the microbial pathogen. Of other host and environmental factors, only an asthma diagnosis was associated with longer duration of illness.

Thus, both viral and bacterial exposure may trigger wheezing episodes in young children, but unidentified host factors may be more important in determining the duration of illness than is the identity of the particular pathogen. Limitations of this study were the lack of isolates from healthy children and data on symptom severity. The study also did not address whether infection or carriage is required and whether upper or lower airway exposure is more important. The conclusion that both bacteria and viruses can be associated with wheezing illnesses in young children is noteworthy clinically, as early childhood wheezing is important in the development of asthma and further atopic disease.

C. J. Carlsson et al., Duration of wheezy episodes in early childhood is independent of the microbial trigger. J. Allergy Clin. Immunol. 10.1016/j.jaci.2015.05.003 (2015). [Abstract]

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