title: Epidemiological and clinical features of respiratory viral infections in hospitalized children during the circulation of influenza virus A(H1N1) 2009.
abstract: BACKGROUND
  Seasonal influenza viruses and respiratory syncytial virus (RSV) are primary causes of acute respiratory tract infections (ARTIs) in children. New respiratory viruses including human metapneumovirus (hMPV), human bocavirus (hBoV), and influenza 2009 A(H1N1) virus have a strong impact on the pediatric population.
  
  
  OBJECTIVE
  To evaluate epidemiological and clinical features of ARTIs in hospitalized children.
  
  
  METHODS
  From December 1, 2008, to December 31, 2009, all children under age fifteen (n = 575) hospitalized for ARTIs were investigated for influenza A (subtype H1N1, H3N2, and 2009 H1N1) and B, RSV A and B, hMPV, and hBoV by PCR.
  
  
  RESULTS
  Fifty-one percent of samples were positive for these respiratory viruses. The frequencies of virus detection were RSV 34·1%, hBoV 6·8%, hMPV 5%, seasonal influenza A 5%, and seasonal influenza B 0%. From April 2009, 11·6% of collected samples were influenza 2009 A(H1N1) positive. Respiratory syncytial virus activity peaked in January, hBoV in February, and hMPV in April. Seasonal influenza A was detected only between January and April 2009, while influenza 2009 A(H1N1) peaked in November. Respiratory syncytial virus and hMPV were mainly associated with lower respiratory tract infections (LRTIs) and with necessity of O(2) administration. The 2009 pandemic influenza was more frequently detected in elder children (P < 0·001) and was associated with higher, longer-lasting fevers compared with other viral infections (P < 0·05).
  
  
  CONCLUSIONS
  All considered viruses were involved in LRTIs. The primary clinical relevance of RSV and a similar involvement of both seasonal influenza and emerging viruses investigated were observed on the pediatric population.
authors.affiliation: Department of Pediatrics, Sacco Hospital, University of Milan, Milan, Italy. gianvincenzo.zuccotti@unimi.it
authors.forename: Gianvincenzo
authors.initials: G
authors.lastname: Zuccotti
authors.forename: Dario
authors.initials: D
authors.lastname: Dilillo
authors.forename: Alessandra
authors.initials: A
authors.lastname: Zappa
authors.forename: Erica
authors.initials: E
authors.lastname: Galli
authors.forename: Antonella
authors.initials: A
authors.lastname: Amendola
authors.forename: Marianna
authors.initials: M
authors.lastname: Martinelli
authors.forename: Elena
authors.initials: E
authors.lastname: Pariani
authors.forename: Filippo
authors.initials: F
authors.lastname: Salvini
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Tanzi
authors.forename: Enrica
authors.initials: E
authors.lastname: Riva
authors.forename: Marcello
authors.initials: M
authors.lastname: Giovannini
mesh_terms: D000293:Adolescent; D002648:Child; D002673:Child, Hospitalized; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D007558:Italy / Q000453:epidemiology; D008297:Male; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000821:virology*; D012621:Seasons; D014780:Viruses / Q000235:genetics / Q000302:isolation & purification*