title: Clinical Characteristics of Pandemic Influenza A (H1N1) 2009 Pediatric Infection in Busan and Gyeongsangnam-do: One Institution.
abstract: BACKGROUND
  This study investigated the clinical characteristics and risk factors of the severity of pandemic influenza A (H1N1) 2009 infection in pediatric patients in Busan and Gyeongsangnam-do.
  
  
  METHODS
  Cases of influenza A (H1N1) 2009 in patients under the age of 18 years, confirmed by reverse transcription polymerase chain reaction, at Pusan National University Hospital and Pusan National University Yangsan Hospital from the last week of August 2009 through the last week of February 2010 were retrospectively analyzed.
  
  
  RESULTS
  Of the 3,777 confirmed cases of influenza A (H1N1) 2009, 2,200 (58.2%) were male and 1,577 (41.8%) were female. The average age of the patients was 8.4±4.8 years. The total cases peaked during 44th to 46th week. Most of the patients were in the 5- to 9-year-old age group. Oseltamivir was administered to 2,959 (78.3%) of the patients. 221 patients (5.9%) were hospitalized, age an average of 6.7±4.5 years. The average duration of hospitalization was 7.4±5.6 days. One hundred cases (45.2%) had pneumonia. Risk factors for hospitalization included male gender, <2 years of age, and underlying disease. Children with asthma were at very high risk of hospitalization, over 20 times the non-asthmatic children (odds ratio [OR], 21.684; confidence interval [CI], 13.295~39.791). Likewise the children with neurologic deficits faced a 16 times higher risk (OR, 15.738; CI, 7.961~31.111). Ten of the patients (4.5%) were admitted to the intensive care unit, and eight (3.6%) required mechanical ventilation.
  
  
  CONCLUSIONS
  Of the pediatric patients with pandemic influenza A (H1N1) 2009, most of the patients were in the 5- to 9-year-old age group. Risk factors for hospitalization included male gender, <2 years of age, and underlying disease. The most common complication was pneumonia. The very high risk of severe morbidity in children with asthma or neurologic disease shows the critical importance of targeted vaccine coverage, special awareness and swift care by both guardians and primary care providers.
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Myung Chul
authors.initials: MC
authors.lastname: Lee
authors.forename: Hye Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Seom Gim
authors.initials: SG
authors.lastname: Kong
authors.forename: Young Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Su Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Young Tak
authors.initials: YT
authors.lastname: Im
authors.forename: Hee Ju
authors.initials: HJ
authors.lastname: Park
keywords: Epidemiologic Study Characteristics as Topic; Influenza A Virus, H1N1 Subtype; Pediatrics