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. 2010 Jul 27;5(7):e11719.
doi: 10.1371/journal.pone.0011719.

Changes in the viral distribution pattern after the appearance of the novel influenza A H1N1 (pH1N1) virus in influenza-like illness patients in Peru

Victor Alberto Laguna-Torres  1 , Jorge Gómez, Patricia V Aguilar, Julia S Ampuero, Cesar Munayco, Víctor Ocaña, Juan Pérez, María E Gamero, Juan Carlos Arrasco, Irmia Paz, Edward Chávez, Rollin Cruz, Jaime Chavez, Silvia Mendocilla, Elizabeth Gomez, Juana Antigoni, Sofía Gonzalez, Cesar Tejada, Gerardo Chowell, Tadeusz J Kochel; Peru Influenza working group
Collaborators, Affiliations

Changes in the viral distribution pattern after the appearance of the novel influenza A H1N1 (pH1N1) virus in influenza-like illness patients in Peru

Victor Alberto Laguna-Torres et al. PLoS One. .

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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. The temporal viral distribution by epidemiological week (EW) in Peru, January 4 to July 13, 2009.
Figure 2
Figure 2. Distribution of viral etiology among regions according to epidemiological week.
Peru, January 4 to July 13, 2009.
Figure 3
Figure 3. Distribution of Influenza A pH1N1 among regions according to epidemiological week.
Peru, May 10 January to July 13, 2009.
Figure 4
Figure 4. Viral etiology before and after the appearance of the novel pH1N1 virus in Peru.
January 4 to July 13 2009. A) Before the appearance of the novel pH1N1 virus, a total of 547 positive results were obtained from 505 positive patients; co-infections were found in 42 samples. B) After the appearance of the novel pH1N1 virus, a total of 767 positive results were obtained from 730 positive patients; co-infections were found in 37 samples.
Figure 5
Figure 5. Distribution of viral etiology across age groups before and after the appearance of the novel pH1N1 virus in Peru, January 4 to July 13, 2009.
A) Before the appearance of pH1N1 virus a total of 544 positive results were obtained from 505 positive patients (missing = 3). B) After the appearance of the pH1N1 a total of 763 positive results were obtained from 730 positive patients (missing  = 4).
See this image and copyright information in PMC

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