RT Journal Article SR Electronic T1 Viruses and asthma exacerbations JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 913 OP 914 DO 10.1136/thx.53.11.913 VO 53 IS 11 A1 N G PAPADOPOULOS A1 S L JOHNSTON YR 1998 UL http://thorax.bmj.com/content/53/11/913.abstract AB