1. Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
2. Copenhagen Prospective Studies on Asthma in Childhood, Faculty of Health Sciences, University of Copenhagen, Copenhagen University Hospital Gentofte, Hellerup, Denmark
3. Department of Food Science, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark
4. Virus & Microbiological Special Diagnostics, Statens Serum Institut, Copenhagen, Denmark
5. Department of Science and Environment, Roskilde University, Roskilde, Denmark