title: Estimated incidence of influenza-virus-associated severe pneumonia in children in El Salvador, 2008-2010.
abstract: OBJECTIVE
  To estimate the incidence of influenza-virus-associated severe pneumonia among Salvadorian children aged < 5 years.
  
  
  METHODS
  Data on children aged < 5 years admitted with severe pneumonia to a sentinel hospital in the western region were collected weekly. Nasal and oropharyngeal swab specimens were collected from a convenience sample of case patients for respiratory virus testing. A health-care utilization survey was conducted in the hospital catchment area to determine the proportion of residents who sought care at the hospital. The incidence of influenza-virus-associated severe pneumonia among all Salvadorian children aged < 5 years was estimated from surveillance and census data, with adjustment for health-care utilization. Influenza virus strains were characterized by the United States Centers for Disease Control and Prevention to determine their correspondence with northern and southern hemisphere influenza vaccine formulations.
  
  
  RESULTS
  Physicians identified 2554 cases of severe pneumonia. Samples from 608 cases were tested for respiratory viruses and 37 (6%) were positive for influenza virus. The estimated incidence of influenza-virus-associated severe pneumonia was 3.2 cases per 1000 person-years (95% confidence interval, CI: 2.8-3.7) overall, 1.5 cases per 1000 person-years (95% CI: 1.0-2.0) during 2008, 7.6 cases per 1000 person-years (95% CI: 6.5-8.9) during 2009 and 0.6 cases per 1000 person-years (95% CI: 0.3-1.0) during 2010. Northern and southern hemisphere vaccine formulations matched influenza virus strains isolated during 2008 and 2010.
  
  
  CONCLUSIONS
  Influenza-virus-associated severe pneumonia occurred frequently among young Salvadorian children during 2008-2010. Antigens in northern and southern hemisphere influenza vaccine formulations corresponded to circulating strains.
authors.affiliation: Centers for Disease Control and Prevention, Central American Region (CDC-CAR), Embassy of the United States in San Salvador El Salvador, Final Blvd Santa Elena, Antiguo Cuscatlan, La Libertad, El Salvador. aclara@gt.cdc.gov
authors.forename: Wilfrido
authors.initials: W
authors.lastname: Clara
authors.forename: Julio
authors.initials: J
authors.lastname: Armero
authors.forename: David
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Celina
authors.initials: C
authors.lastname: de Lozano
authors.forename: Luis
authors.initials: L
authors.lastname: Bonilla
authors.forename: Percy
authors.initials: P
authors.lastname: Minaya
authors.forename: Rafael
authors.initials: R
authors.lastname: Chacón
authors.forename: Jorge
authors.initials: J
authors.lastname: Jara
authors.forename: Natalia
authors.initials: N
authors.lastname: Blanco
authors.forename: Marc-Alain
authors.initials: MA
authors.lastname: Widdowson
authors.forename: Joseph
authors.initials: J
authors.lastname: Bresee
authors.forename: Xiyan
authors.initials: X
authors.lastname: Xu
authors.forename: Alexander
authors.initials: A
authors.lastname: Klimov
authors.forename: Eduardo
authors.initials: E
authors.lastname: Azziz-Baumgartner
authors.forename: Nivaldo
authors.initials: N
authors.lastname: Linares-Perez
mesh_terms: D002675:Child, Preschool; D004544:El Salvador / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity; D007251:Influenza, Human / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D008297:Male; D009093:Mucus / Q000821:virology; D011024:Pneumonia, Viral / Q000453:epidemiology* / Q000209:etiology / Q000821:virology; D012720:Severity of Illness Index