title: Clinical and socioeconomic impact of different types and subtypes of seasonal influenza viruses in children during influenza seasons 2007/2008 and 2008/2009.
abstract: BACKGROUND
  There are few and debated data regarding possible differences in the clinical presentations of influenza A/H1N1, A/H3N2 and B viruses in children. This study evaluates the clinical presentation and socio-economic impact of laboratory-confirmed influenza A/H1N1, A/H3N2 or B infection in children attending an Emergency Room because of influenza-like illness.
  
  
  METHODS
  Among the 4,726 children involved, 662 had influenza A (143 A/H1N1 and 519 A/H3N2) and 239 influenza B infection detected by means of real-time polymerase chain reaction. Upon enrollment, systematic recordings were made of the patients' demographic characteristics and medical history using standardised written questionnaires. The medical history of the children was re-evaluated 5-7 days after enrollment and until the resolution of their illness by means of interviews and a clinical examination by trained investigators using standardised questionnaires. During this evaluation, information was also obtained regarding illnesses and related morbidity among households.
  
  
  RESULTS
  Children infected with influenza A/H1N1 were significantly younger (mean age, 2.3 yrs) than children infected with influenza A/H3N2 (mean age, 4.7 yrs; p < 0.05)) or with influenza B (mean age, 5.2 yrs; p < 0.05). Adjusted for age and sex, children with influenza A/H3N2 in comparison with those infected by either A/H1N1 or with B influenza virus were more frequently affected by fever (p < 0.05) and lower respiratory tract involvement (p < 0.05), showed a worse clinical outcome (p < 0.05), required greater drug use (p < 0.05), and suffered a worse socio-economic impact (p < 0.05). Adjusted for age and sex, children with influenza B in comparison with those infected by A/H1N1 influenza virus had significantly higher hospitalization rates (p < 0.05), the households with a disease similar to that of the infected child (p < 0.05) and the need for additional household medical visits (p < 0.05).
  
  
  CONCLUSIONS
  Disease due to influenza A/H3N2 viral subtype is significantly more severe than that due to influenza A/H1N1 subtype and influenza B virus, which indicates that the characteristics of the different viral types and subtypes should be adequately considered by health authorities when planning preventive and therapeutic measures.
authors: Department of Maternal and Pediatric Sciences, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. susanna.esposito@unimi.it
authors: Susanna
authors: S
authors: Esposito
authors: Claudio Giuseppe
authors: CG
authors: Molteni
authors: Cristina
authors: C
authors: Daleno
authors: Antonia
authors: A
authors: Valzano
authors: Emilio
authors: E
authors: Fossali
authors: Liviana
authors: L
authors: Da Dalt
authors: Valerio
authors: V
authors: Cecinati
authors: Eugenia
authors: E
authors: Bruzzese
authors: Raffaella
authors: R
authors: Giacchino
authors: Carlo
authors: C
authors: Giaquinto
authors: Angie
authors: A
authors: Lackenby
authors: Nicola
authors: N
authors: Principi
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D053122:Influenza A Virus, H3N2 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D009981:Influenza B virus / Q000302:isolation & purification* / Q000472:pathogenicity; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology*; D008297:Male; D008487:Medical History Taking; D011446:Prospective Studies; D012367:RNA, Viral / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012307:Risk Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires
chemical_list: D012367:RNA, Viral