Intended for healthcare professionals

CCBYNC Open access

Association of bacteria and viruses with wheezy episodes in young children: prospective birth cohort study

BMJ 2010; 341 doi: (Published 04 October 2010) Cite this as: BMJ 2010;341:c4978

This article has a correction. Please see:

  1. Hans Bisgaard, professor1,
  2. Mette Northman Hermansen, medical doctor1,
  3. Klaus Bønnelykke, senior scientist1,
  4. Jakob Stokholm, research doctor, PhD student1,
  5. Florent Baty, statistician1,
  6. Nanna Lassen Skytt, junior scientist1,
  7. Julia Aniscenko, research technician2,
  8. Tatiana Kebadze, technician2,
  9. Sebastian L Johnston, professor2
  1. 1The Copenhagen Prospective Studies on Asthma in Childhood; Health Sciences, University of Copenhagen, and The Danish Pediatric Asthma Centre; Copenhagen University Hospital, Gentofte, Ledreborg Allé 34, DK-2820 Gentofte, Copenhagen, Denmark
  2. 2Department of Respiratory Medicine, National Heart and Lung Institute, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, and Centre for Respiratory Infection, Imperial College London, UK
  1. Correspondence to: H Bisgaard Bisgaard{at}
  • Accepted 12 July 2010


Objective To study the association between wheezy symptoms in young children and the presence of bacteria in the airways.

Design Birth cohort study.

Setting Clinical research unit in Copenhagen.

Participants Children of asthmatic mothers, from age 4 weeks to 3 years, with planned visits and acute admissions to the research clinic.

Main outcome measure Frequency of bacteria and virus carriage in airway aspirates during wheezy episodes and at planned visits without respiratory symptoms.

Results 984 samples (361 children) were analysed for bacteria, 844 (299 children) for viruses, and 696 (277 children) for both viruses and bacteria. Wheezy episodes were associated with both bacterial infection (odds ratio 2.9, 95% confidence interval 1.9 to 4.3; P<0.001) and virus infection (2.8, 1.7 to 4.4; P<0.001). The associations of bacteria and viruses were independent of each other.

Conclusion Acute wheezy episodes in young children were significantly associated with bacterial infections similar to but independent of the association with virus infections.


  • We thank the participating children and parents, the Copenhagen Prospective Study on Asthma in Childhood study teams, and Tobias Allander for his assistance with the polymerase chain reaction of bocavirus.

  • Contributors: HB was responsible for the integrity of the work, from conception and design to conduct of the study; the acquisition, analysis, and interpretation of the data; and drafting of the manuscript. He had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. HB is guarantor. MNH contributed to the data acquisition, data analyses and helped write the manuscript. KB and JS contributed to data analyses and interpretation and helped write the manuscript. FB did the statistical analyses. NLS contributed to data acquisition. SLJ was responsible for the analyses of the viruses and helped write the manuscript. JA and TK contributed to the analyses of viruses. All authors provided important intellectual input and approved the final version of the manuscript.

  • Funding: The Copenhagen Prospective Study on Asthma in Childhood is funded by private and public research funds (see The study is supported by the Lundbeck Foundation, the Pharmacy Foundation of 1991, Augustinus Foundation, the Danish Medical Research Council, and the Danish Pediatric Asthma Centre. The funding agencies had no role in the study design; the conduct of the study; data collection and management; data analysis; or the preparation, review, or approval of the manuscript.

  • All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: no support from any company for the submitted work; no financial relationships with any companies that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the ethics committee for Copenhagen (KF 01-289/96 and KF 11-107/02) and the Danish Data Protection Agency (2008-41-1754).

  • Data sharing: The technical appendix, statistical code, and dataset are available from the corresponding author at Bisgaard{at}

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

View Full Text