title: Changes in the viral distribution pattern after the appearance of the novel influenza A H1N1 (pH1N1) virus in influenza-like illness patients in Peru.
abstract: BACKGROUND
  We describe the temporal variation in viral agents detected in influenza like illness (ILI) patients before and after the appearance of the ongoing pandemic influenza A (H1N1) (pH1N1) in Peru between 4-January and 13-July 2009.
  
  
  METHODS
  At the health centers, one oropharyngeal swab was obtained for viral isolation. From epidemiological week (EW) 1 to 18, at the US Naval Medical Research Center Detachment (NMRCD) in Lima, the specimens were inoculated into four cell lines for virus isolation. In addition, from EW 19 to 28, the specimens were also analyzed by real time-polymerase-chain-reaction (rRT-PCR).
  
  
  RESULTS
  We enrolled 2,872 patients: 1,422 cases before the appearance of the pH1N1 virus, and 1,450 during the pandemic. Non-pH1N1 influenza A virus was the predominant viral strain circulating in Peru through (EW) 18, representing 57.8% of the confirmed cases; however, this predominance shifted to pH1N1 (51.5%) from EW 19-28. During this study period, most of pH1N1 cases were diagnosed in the capital city (Lima) followed by other cities including Cusco and Trujillo. In contrast, novel influenza cases were essentially absent in the tropical rain forest (jungle) cities during our study period. The city of Iquitos (Jungle) had the highest number of influenza B cases and only one pH1N1 case.
  
  
  CONCLUSIONS
  The viral distribution in Peru changed upon the introduction of the pH1N1 virus compared to previous months. Although influenza A viruses continue to be the predominant viral pathogen, the pH1N1 virus predominated over the other influenza A viruses.
authors.affiliation: Virology Department, United States Naval Medical Research Center Detachment, Lima, Perú. alberto.laguna@med.navy.mil
authors.forename: Victor Alberto
authors.initials: VA
authors.lastname: Laguna-Torres
authors.forename: Jorge
authors.initials: J
authors.lastname: Gómez
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Aguilar
authors.forename: Julia S
authors.initials: JS
authors.lastname: Ampuero
authors.forename: Cesar
authors.initials: C
authors.lastname: Munayco
authors.forename: Víctor
authors.initials: V
authors.lastname: Ocaña
authors.forename: Juan
authors.initials: J
authors.lastname: Pérez
authors.forename: María E
authors.initials: ME
authors.lastname: Gamero
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Arrasco
authors.forename: Irmia
authors.initials: I
authors.lastname: Paz
authors.forename: Edward
authors.initials: E
authors.lastname: Chávez
authors.forename: Rollin
authors.initials: R
authors.lastname: Cruz
authors.forename: Jaime
authors.initials: J
authors.lastname: Chavez
authors.forename: Silvia
authors.initials: S
authors.lastname: Mendocilla
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Gomez
authors.forename: Juana
authors.initials: J
authors.lastname: Antigoni
authors.forename: Sofía
authors.initials: S
authors.lastname: Gonzalez
authors.forename: Cesar
authors.initials: C
authors.lastname: Tejada
authors.forename: Gerardo
authors.initials: G
authors.lastname: Chowell
authors.forename: Tadeusz J
authors.initials: TJ
authors.lastname: Kochel
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D010568:Peru / Q000453:epidemiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult