title: [Enhanced surveillance of initial cases of pandemic influenza (H1N1) 2009 infection in Spain, April-June 2009].
abstract: BACKGROUND
  In April 2009, a new surveillance strategy for the detection of cases of pandemic influenza (H1N1) 2009 infection and for the implementation of appropriate control measures to contain its transmission was initiated in Spain. We describe the clinical and epidemiological characteristics of confirmed cases in Spain notified by the National Epidemiological Surveillance Network from April 24 to June 30, 2009.
  
  
  METHODS
  As part of the initial surveillance response to the pandemic, case-based clinical and epidemiological information was collected nationwide on cases under investigation for pandemic virus (H1N1) 2009 infection and their contacts.
  
  
  RESULTS
  Of 717 confirmed cases, 91% were notified by 5 Autonomous Communities. As of June 15,49.1% of cases belonged to school outbreaks. No nosocomial outbreaks were detected. The median incubation period was 3 days. Eighty-eight percent of cases were under the age of 30 years, and 24.9% were imported. The most frequent symptoms were cough (92%) and fever (81.8%). The median duration of symptoms was 5 days. Thirteen cases required hospitalization and one died.
  
  
  CONCLUSIONS
  During the first months of the pandemic, pandemic influenza cases experienced a mild illness similar to seasonal influenza, predominantly affecting children and young adults. By the end of June 2009, the detection of outbreaks in different settings indicated the diffusion of the pandemic virus into the community and the start of its circulation.
authors.affiliation: Centro de Coordinación de Alertas y Emergencias Sanitarias (CCAES), Dirección General de Salud Pública y Sanidad Exterior, Ministerio de Sanidad y Política Social de España, Madrid, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Santa-Olalla Peralta
authors.forename: Marta
authors.initials: M
authors.lastname: Cortes García
authors.forename: Elena Vanessa
authors.initials: EV
authors.lastname: Martínez Sánchez
authors.forename: Francisco
authors.initials: F
authors.lastname: Nogareda Moreno
authors.forename: Aurora
authors.initials: A
authors.lastname: Limia Sánchez
authors.forename: Isabel
authors.initials: I
authors.lastname: Pachón Del Amo
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Sierra Moros
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D011159:Population Surveillance / Q000379:methods*; D011996:Records; D013030:Spain / Q000453:epidemiology; D013997:Time Factors; D055815:Young Adult