Badarchiin Darmaa¹, SosorburamiinTsatsral¹, Tsedenbalyn Naranzul¹, Nymadawagiin Naranbold ¹, Dashdondogiin Enkhsaikhan¹, Alexanderiin Burmaa¹ and Pagbajabyn Nymadawa ²

 National Center of Communicable Diseases, Ulaanbaatar, Mongolia­­­­­­­­­­­­­­­¹

Mongolian Academy of Medical Science²

Abstract

The purpose of this study was to characterize the antigenic and genetic relationships among influenza viruses isolated in Mongolia during the 2003-2007. We collected 7073 clinical samples for influenza virus isolation and 691 (9.8%) of them were positive. Of these, 334 (48.3%) were positive for influenza A viruses, and 357 (51.7%) for influenza B viruses. The influenza A viruses peaked during winter season every year throughout the study period, and influenza B viruses were isolated from March to early April in 2007. The circulating A (H3N2) strains matched the corresponding vaccine strain in 2003/04 and 2005/06.  However, several A(H3N2) isolates did not react well with reference serum. Phylogenetic analyses of the HA gene showed that antigenic of drift variants occurred among A (H3N2) influenza strains in the last four influenza season.

Although there are 2 genetically distinct clusters of influenza B viruses including Victoria-lineages (B/Malyasia/2506/2004) and Yamagata-lineage (B/Florida/7/2004), most of the Mongolian B isolates were closely related to B/Malyasia/2506/2004 which is the-WHO recommended vaccine strain 2007/2008 in Northern hemisphere.

We supposed that whole genome sequence analyses would help in elucidating the mutational changes in PB2, PA, NP and NS which may play a role to change the virulence and transmissibility of influenza viruses.