Influenza activity in Cambodia during 2006-2008

Sek Mardy,Sovann Ly,Duong Veasna,Chea Huch,Sok Touch,Megge Miller,Nima Asgari,Isabelle Bergeri,Weigong Zhou,Philippe Buchy,Seng Heng,Sirenda Vong,Takeshi Kasai,Chea Nora,Sybille Rehmet

doi:10.1186/1471-2334-9-168

Abstract

BackgroundThere is little information about influenza disease among the Cambodian population. To better understand the dynamics of influenza in Cambodia, the Cambodian National Influenza Center (NIC) was established in August 2006. To continuously monitor influenza activity, a hospital based sentinel surveillance system for ILI (influenza like illness) with a weekly reporting and sampling scheme was established in five sites in 2006. In addition, hospital based surveillance of acute lower respiratory infection (ALRI) cases was established in 2 sites.MethodsThe sentinel sites collect weekly epidemiological data on ILI patients fulfilling the case definition, and take naso-pharyngeal specimens from a defined number of cases per week. The samples are tested in the Virology Unit at the Institut Pasteur in Phnom Penh. From each sample viral RNA was extracted and amplified by a multiplex RT-PCR detecting simultaneously influenza A and influenza B virus. Influenza A viruses were then subtyped and analyzed by hemagglutination inhibition assay. Samples collected by the ALRI system were tested with the same approach.ResultsFrom 2006 to 2008, influenza circulation was observed mainly from June to December, with a clear seasonal peak in October shown in the data from 2008.ConclusionInfluenza activity in Cambodia occurred during the rainy season, from June to December, and ended before the cool season (extending usually from December to February). Although Cambodia is a tropical country geographically located in the northern hemisphere, influenza activity has a southern hemisphere transmission pattern. Together with the antigenic analysis of the circulating strains, it is now possible to give better influenza vaccination recommendation for Cambodia.

Highlights

There is little information about influenza disease among the Cambodian population
We summarize in this report data gathered from the Cambodian National Influenza Center (NIC) which is based on sampling ILI patients from 5 sentinel outpatients' departments located across the country
This study provides the first data regarding influenza activity in Cambodia, combining influenza-like illness surveillance and acute lower respiratory infection surveillance

Summary

Introduction

To better understand the dynamics of influenza in Cambodia, the Cambodian National Influenza Center (NIC) was established in August 2006. To better describe the epidemiology, seasonality and disease burden of influenza as well as to minimize the impact of this disease, the World Health Organization (WHO) formed an Influenza Surveillance Network to detect the emergence and spread of new influenza antigenic variants, to use circulating strains characteristics information to update the formulation of influenza vaccine, and to provide as much warning as possible of the pandemic. In 1952, WHO established an international laboratory-based surveillance network for influenza. The network currently consists of 125 National Influenza Centre (NIC) laboratories in 95 countries, and four WHO Collaborating Centers for Reference and Research on Influenza (WHO CC) [4]

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