Changes in the viral distribution pattern after the appearance of the novel influenza A H1N1 (pH1N1) virus in influenza-like illness patients in Peru.
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.
Laguna-Torres
Victor Alberto
VA
Virology Department, United States Naval Medical Research Center Detachment, Lima, Perú. alberto.laguna@med.navy.mil
Gómez
Jorge
J
Aguilar
Patricia V
PV
Ampuero
Julia S
JS
Munayco
Cesar
C
Ocaña
Víctor
V
Pérez
Juan
J
Gamero
María E
ME
Arrasco
Juan Carlos
JC
Paz
Irmia
I
Chávez
Edward
E
Cruz
Rollin
R
Chavez
Jaime
J
Mendocilla
Silvia
S
Gomez
Elizabeth
E
Antigoni
Juana
J
Gonzalez
Sofía
S
Tejada
Cesar
C
Chowell
Gerardo
G
Kochel
Tadeusz J
TJ
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