Sentinel surveillance of influenza-like-illness in two cities of the tropical country of Ecuador: 2006-2010.

Richard W Douce,Wilson Chicaiza-Ayala,Josefina Garcia,Julia Ampuero,Mireya Rodas,Franklin Delgado,Tadeusz Kochel,Gloria Chauca,Washington Aleman,V Alberto Laguna-Torres,Eric S Halsey,Merly Sovero,Cesar Madrid,Juan Perez,Patricia V Aguilar

doi:10.1371/journal.pone.0022206

Abstract

BackgroundTropical countries are thought to play an important role in the global behavior of respiratory infections such as influenza. The tropical country of Ecuador has almost no documentation of the causes of acute respiratory infections. The objectives of this study were to identify the viral agents associated with influenza like illness (ILI) in Ecuador, describe what strains of influenza were circulating in the region along with their epidemiologic characteristics, and perform molecular characterization of those strains.Methodology/FindingsThis is a prospective surveillance study of the causes of ILI based on viral culture of oropharyngeal specimens and case report forms obtained in hospitals from two cities of Ecuador over 4 years. Out of 1,702 cases of ILI, nine viral agents were detected in 597 patients. During the time of the study, seven genetic variants of influenza circulated in Ecuador, causing six periods of increased activity. There appeared to be more heterogeneity in the cause of ILI in the tropical city of Guayaquil when compared with the Andean city of Quito.Conclusions/SignificanceThis was the most extensive documentation of the viral causes of ILI in Ecuador to date. Influenza was a common cause of ILI in Ecuador, causing more than one outbreak per year. There was no well defined influenza season although there were periods of time when no influenza was detected alternating with epidemics of different variant strains.

Highlights

In an effort to control influenza A by early detection of potentially epidemic strains for vaccine production, the behavior of influenza A on a global scale has become very important [1]
The specimens submitted on the first day of symptoms were 1.5 times (Odds Ratio = 1.494, 95%confidence intervals (CI) 1.191–1.874) more likely to have positive results compared with samples taken on subsequent days
The results of this study are consistent with other studies of influenza in tropical countries [3] where there is little seasonal variation in climate, and it is more difficult to define an influenza season [4,22,23]

Summary

Introduction

In an effort to control influenza A by early detection of potentially epidemic strains for vaccine production, the behavior of influenza A on a global scale has become very important [1]. Many authors have sought to link the behavior of influenza epidemics in the tropics to environmental factors, no dominant hypothesis seems to explain the varied seasonal activity of influenza in the tropics [5]. The other hypothesis is that there is constant latent viral activity in the tropics that seeds the hemispheric seasonal epidemics and that the viral genetic diversity of influenza A is generated in the tropics and is transmitted to the temperate regions [7]. Understanding influenza activity in the tropics may help predict the global behavior of specific strains and aid in the selection of vaccine strains. Tropical countries are thought to play an important role in the global behavior of respiratory infections such as influenza. The objectives of this study were to identify the viral agents associated with influenza like illness (ILI) in Ecuador, describe what strains of influenza were circulating in the region along with their epidemiologic characteristics, and perform molecular characterization of those strains

Objectives

Methods

Results

Conclusion