title: Role of respiratory viruses in acute upper and lower respiratory tract illness in the first year of life: a birth cohort study.
abstract: BACKGROUND
  Although acute respiratory illnesses (ARI) are major causes of morbidity and mortality in early childhood worldwide, little progress has been made in their control and prophylaxis. Most studies have focused on hospitalized children or children from closed populations. It is essential that the viral etiology of these clinical diseases be accurately defined in the development of antiviral drugs.
  
  
  OBJECTIVE
  To investigate the role of all common respiratory viruses as upper and lower respiratory tract pathogens in the first year of life.
  
  
  METHODS
  This community-based birth cohort study prospectively collected detailed information on all ARI contracted by 263 infants from birth until 1 year of age. Nasopharyngeal aspirates were collected for each ARI episode, and all common respiratory viruses were detected by polymerase chain reaction. Episodes were classified as upper respiratory illnesses or lower respiratory illnesses (LRI), with or without wheeze.
  
  
  RESULTS
  The majority reported 2-5 episodes of ARI in the first year (range, 0-11 episodes; mean, 4.1). One-third were LRI, and 29% of these were associated with wheeze. Viruses were detected in 69% of ARI; most common were rhinoviruses (48.5%) and respiratory syncytial virus (RSV) (10.9%). Compared with RSV, >10 times the number of upper respiratory illnesses and >3 times the number of both LRI and wheezing LRI were attributed to rhinoviruses.
  
  
  CONCLUSIONS
  Rhinoviruses are the major upper and lower respiratory pathogens in the first year of life. Although RSV is strongly associated with severe LRI requiring hospitalization, the role of rhinoviruses as the major lower respiratory pathogens in infants has not previously been recognized.
authors.affiliation: Division of Clinical Sciences, Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, West Perth, Australia. mercik@ichr.uwa.edu.au
authors.forename: Merci M H
authors.initials: MM
authors.lastname: Kusel
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: de Klerk
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Holt
authors.forename: Tatiana
authors.initials: T
authors.lastname: Kebadze
authors.forename: Sebastian L
authors.initials: SL
authors.lastname: Johnston
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sly
mesh_terms: D000208:Acute Disease; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology; D012136:Respiratory Syncytial Viruses / Q000302:isolation & purification; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000821:virology*; D012229:Rhinovirus / Q000302:isolation & purification; D014904:Western Australia / Q000453:epidemiology