sharon sanders
Editor-in-Chief & President
Genetic Analysis of Influenza A/H3N2 and A/H1N1 Viruses Circulating in Vietnam from 2001 to 2006<sup>
</sup>
Danjuan Li,<sup>1</sup><sup>*</sup> Reiko Saito,<sup>1</sup> Mai T. Q. Le,<sup>2</sup> Hang L. K. Nguyen,<sup>2</sup> Yasushi Suzuki,<sup>1</sup> Yugo Shobugawa,<sup>1</sup> Duc T. Dinh,<sup>2</sup> Phuong V. M. Hoang,<sup>2</sup> Huong T. T. Tran,<sup>2</sup> Ha K. Nghiem,<sup>2</sup> Long T. Hoang,<sup>2</sup> Lien P. Huynh,<sup>2</sup> Hien T. Nguyen,<sup>2</sup> Makoto Nishikawa,<sup>3</sup> and Hiroshi Suzuki<sup>1</sup> Department of Public Health, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan,<sup>1</sup> National Institute of Hygiene and Epidemiology, Hanoi, Vietnam,<sup>2</sup> Niigata Prefectural Institute of Public Health and Environmental Sciences, Niigata City, Niigata Prefecture, Japan<sup>3</sup>
Received 3 August 2007/ Returned for modification 13 September 2007/ Accepted 10 October 2007
<!-- ABS --> Influenza A virus has the ability to overcome immunity from<sup> </sup>previous infections through the acquisition of genetic changes.<sup> </sup>Thus, understanding the evolution of the viruses in humans is<sup> </sup>important for the surveillance and the selection of vaccine<sup> </sup>strains. A total of 30 influenza A/H3N2 viruses and 35 influenza<sup> </sup>A/H1N1 viruses that were collected in Vietnam from 2001 to 2006<sup> </sup>were used to analyze the evolution of the hemagglutinin (HA),<sup> </sup>neuraminidase (NA), and matrix protein (M) genes. Phylogenetic<sup> </sup>analysis of individual gene segments revealed that the HA and<sup> </sup>the NA genes of the influenza A viruses evolved in a sequential<sup> </sup>way. However, the evolutionary pattern of the M gene proved<sup> </sup>to be nonlinear and was not linked with that of the HA and NA<sup> </sup>genes. Genetic drift in HA1 segments, especially in the antigenic<sup> </sup>sites of A/H3N2 viruses, occurred more frequently in A/H3N2<sup> </sup>viruses than it did in A/H1N1 viruses. Two reassortants, one<sup> </sup>influenza A/H3N2 strain and one A/H1N1 strain, were found on<sup> </sup>the basis of the phylogenetic analysis of the three genes. While<sup> </sup>both genetic mutation and reassortment contributed to their<sup> </sup>evolution, the frequency of genetic changes and reassortment<sup> </sup>events differs between the two subtypes. As influenza viruses<sup> </sup>circulate throughout the year, we emphasize the importance of<sup> </sup>surveillance in tropical and subtropical zones, where the emergence<sup> </sup>of new strains may be detected earlier than it is in temperate<sup> </sup>zones.
http://jcm.asm.org/cgi/content/abstract/46/2/399
Danjuan Li,<sup>1</sup><sup>*</sup> Reiko Saito,<sup>1</sup> Mai T. Q. Le,<sup>2</sup> Hang L. K. Nguyen,<sup>2</sup> Yasushi Suzuki,<sup>1</sup> Yugo Shobugawa,<sup>1</sup> Duc T. Dinh,<sup>2</sup> Phuong V. M. Hoang,<sup>2</sup> Huong T. T. Tran,<sup>2</sup> Ha K. Nghiem,<sup>2</sup> Long T. Hoang,<sup>2</sup> Lien P. Huynh,<sup>2</sup> Hien T. Nguyen,<sup>2</sup> Makoto Nishikawa,<sup>3</sup> and Hiroshi Suzuki<sup>1</sup> Department of Public Health, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan,<sup>1</sup> National Institute of Hygiene and Epidemiology, Hanoi, Vietnam,<sup>2</sup> Niigata Prefectural Institute of Public Health and Environmental Sciences, Niigata City, Niigata Prefecture, Japan<sup>3</sup>
Received 3 August 2007/ Returned for modification 13 September 2007/ Accepted 10 October 2007
<!-- ABS --> Influenza A virus has the ability to overcome immunity from<sup> </sup>previous infections through the acquisition of genetic changes.<sup> </sup>Thus, understanding the evolution of the viruses in humans is<sup> </sup>important for the surveillance and the selection of vaccine<sup> </sup>strains. A total of 30 influenza A/H3N2 viruses and 35 influenza<sup> </sup>A/H1N1 viruses that were collected in Vietnam from 2001 to 2006<sup> </sup>were used to analyze the evolution of the hemagglutinin (HA),<sup> </sup>neuraminidase (NA), and matrix protein (M) genes. Phylogenetic<sup> </sup>analysis of individual gene segments revealed that the HA and<sup> </sup>the NA genes of the influenza A viruses evolved in a sequential<sup> </sup>way. However, the evolutionary pattern of the M gene proved<sup> </sup>to be nonlinear and was not linked with that of the HA and NA<sup> </sup>genes. Genetic drift in HA1 segments, especially in the antigenic<sup> </sup>sites of A/H3N2 viruses, occurred more frequently in A/H3N2<sup> </sup>viruses than it did in A/H1N1 viruses. Two reassortants, one<sup> </sup>influenza A/H3N2 strain and one A/H1N1 strain, were found on<sup> </sup>the basis of the phylogenetic analysis of the three genes. While<sup> </sup>both genetic mutation and reassortment contributed to their<sup> </sup>evolution, the frequency of genetic changes and reassortment<sup> </sup>events differs between the two subtypes. As influenza viruses<sup> </sup>circulate throughout the year, we emphasize the importance of<sup> </sup>surveillance in tropical and subtropical zones, where the emergence<sup> </sup>of new strains may be detected earlier than it is in temperate<sup> </sup>zones.
http://jcm.asm.org/cgi/content/abstract/46/2/399