title: Lower airway rhinovirus burden and the seasonal risk of asthma exacerbation.
abstract: BACKGROUND
  Most asthma exacerbations are initiated by viral upper respiratory illnesses. It is unclear whether human rhinovirus (HRV)–induced exacerbations are associated with greater viral replication and neutrophilic inflammation compared with HRV colds.
  
  
  OBJECTIVE
  To evaluate viral strain and load in a prospective asthma cohort during a natural cold.
  
  
  METHODS
  Adults were enrolled at the first sign of a cold, with daily monitoring of symptoms, medication use, and peak expiratory flow rate until resolution. Serial nasal lavage and induced sputum samples were assessed for viral copy number and inflammatory cell counts.
  
  
  RESULTS
  A total of 52 persons with asthma and 14 control subjects without atopy or asthma were studied for over 10 weeks per subject on average; 25 participants developed an asthma exacerbation. Detection of HRVs in the preceding 5 days was the most common attributable exposure related to exacerbation. Compared with other infections, those by a minor group A HRV were 4.4- fold more likely to cause exacerbation (P = 0.038). Overall, sputum neutrophils and the burden of rhinovirus in the lower airway were similar in control subjects without atopy and the asthma group. However, among HRV-infected participants with asthma, exacerbations were associated with greater sputum neutrophil counts (P = 0.005).
  
  
  CONCLUSIONS
  HRV infection is a frequent cause of exacerbations in adults with asthma and a cold, and there may be group-specific differences in severity of these events. The absence of large differences in viral burden among groups suggests differential lower airway sensitization to the effects of neutrophilic inflammation in the patients having exacerbations.
authors.affiliation: Department of Medicine-Allergy, Pulmonary & Critical Care, University of Wisconsin-Madison, 53792, USA. lcd@medicine.wisc.edu
authors.forename: Loren C
authors.initials: LC
authors.lastname: Denlinger
authors.forename: Ron L
authors.initials: RL
authors.lastname: Sorkness
authors.forename: Wai-Ming
authors.initials: WM
authors.lastname: Lee
authors.forename: Michael D
authors.initials: MD
authors.lastname: Evans
authors.forename: Michele J
authors.initials: MJ
authors.lastname: Wolff
authors.forename: Sameer K
authors.initials: SK
authors.lastname: Mathur
authors.forename: Gina M
authors.initials: GM
authors.lastname: Crisafi
authors.forename: Katie L
authors.initials: KL
authors.lastname: Gaworski
authors.forename: Tressa E
authors.initials: TE
authors.lastname: Pappas
authors.forename: Rose F
authors.initials: RF
authors.lastname: Vrtis
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Kelly
authors.forename: James E
authors.initials: JE
authors.lastname: Gern
authors.forename: Nizar N
authors.initials: NN
authors.lastname: Jarjour
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000276:immunology / Q000821:virology*; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D007249:Inflammation / Q000150:complications; D007958:Leukocyte Count; D008297:Male; D055556:Nasal Lavage; D009504:Neutrophils; D010366:Peak Expiratory Flow Rate; D010850:Picornaviridae Infections / Q000150:complications*; D011446:Prospective Studies; D012008:Recurrence; D012137:Respiratory System / Q000821:virology; D012229:Rhinovirus / Q000302:isolation & purification*; D012621:Seasons; D012720:Severity of Illness Index; D013183:Sputum / Q000166:cytology / Q000821:virology*; D019562:Viral Load