Circulation of human influenza viruses and emergence of Oseltamivir-resistant A(H1N1) viruses in Cameroon, Central Africa

Richard Njouom,Victoria Gregory,Dominique Noah Noah,Patrick Collins,Pierre Cappy,Dominique Rousset,Alan Hay,Serge A Sadeuh Mba

doi:10.1186/1471-2334-10-56

Abstract

BackgroundWhile influenza surveillance has increased in most developing countries in the last few years, little influenza surveillance has been carried out in sub-Saharan Africa and no information is available in Central Africa. The objective of this study was to assess the prevalence of influenza viruses circulating in Yaounde, Cameroon and determine their antigenic and genetic characteristics.MethodsThroat and/or nasal swabs were collected from November 2007 to October 2008 from outpatients with influenza-like illness (ILI) in Yaounde, Cameroon and analyzed by two different techniques: a one-step real time reverse transcription-polymerase chain reaction (RT-PCR) and virus isolation in MDCK cells. Typing and subtyping of virus isolates was performed by hemagglutination inhibition (HI), and viruses were sent to the WHO Collaborating Centre in London, UK for further characterization and analyses of antiviral resistance by enzyme inhibition assay and nucleotide sequencing.ResultsA total of 238 patients with ILI were sampled. During this period 70 (29%) samples were positive for influenza by RT-PCR, of which only 26 (11%) were positive by virus isolation. By HI assay, 20 of the 26 isolates were influenza type A (10 H3N2 and 10 H1N1) and 6 were influenza type B (2 B/Victoria/2/87 lineage and 4 B/Yagamata/16/88 lineage). Seven (70%) of the H1N1 isolates were shown to be resistant to oseltamivir due to a H275Y mutation.ConclusionsThis study confirmed the circulation of influenza A(H1N1), A(H3N2) and B viruses in the human population in Central Africa and describes the emergence of oseltamivir-resistant A(H1N1) viruses in Central Africa.

Highlights

While influenza surveillance has increased in most developing countries in the last few years, little influenza surveillance has been carried out in sub-Saharan Africa and no information is available in Central Africa
Serotyping of virus isolates was performed by hemagglutination inhibition (HI) assay using human group O red blood cells and 2007 reference reagents for influenza virus diagnosis from a WHO kit provided by the Center for Disease Control (CDC), Atlanta
Seventy (29%) samples were positive for influenza by reverse transcription-polymerase chain reaction (RT-PCR), of which only 26 (11%) were positive by virus isolation

Summary

Introduction

While influenza surveillance has increased in most developing countries in the last few years, little influenza surveillance has been carried out in sub-Saharan Africa and no information is available in Central Africa. Highly contagious respiratory infection that can cause very serious illness [1]. Identification and characterization of circulating influenza viruses is essential to detect the emergence of antigenic drift variants causing influenza epidemics and novel A subtypes with the potential to cause an influenza pandemic [2]. Influenza surveillance provides a basis for selection of the virus strains to be included in the annual formulation of influenza vaccines [3,4]. The recent emergence of new highly virulent influenza A(H5N1) viruses, their wide circulation in wild and domestic birds and the associated human

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