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Journal of Clinical Microbiology, February 2008, p. 399-405, Vol. 46, No. 2
0095-1137/08/$08.00+0     doi:10.1128/JCM.01549-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic Analysis of Influenza A/H3N2 and A/H1N1 Viruses Circulating in Vietnam from 2001 to 2006{triangledown}

Danjuan Li,1* Reiko Saito,1 Mai T. Q. Le,2 Hang L. K. Nguyen,2 Yasushi Suzuki,1 Yugo Shobugawa,1 Duc T. Dinh,2 Phuong V. M. Hoang,2 Huong T. T. Tran,2 Ha K. Nghiem,2 Long T. Hoang,2 Lien P. Huynh,2 Hien T. Nguyen,2 Makoto Nishikawa,3 and Hiroshi Suzuki1

Department of Public Health, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan,1 National Institute of Hygiene and Epidemiology, Hanoi, Vietnam,2 Niigata Prefectural Institute of Public Health and Environmental Sciences, Niigata City, Niigata Prefecture, Japan3

Received 3 August 2007/ Returned for modification 13 September 2007/ Accepted 10 October 2007

Influenza A virus has the ability to overcome immunity from previous infections through the acquisition of genetic changes. Thus, understanding the evolution of the viruses in humans is important for the surveillance and the selection of vaccine strains. A total of 30 influenza A/H3N2 viruses and 35 influenza A/H1N1 viruses that were collected in Vietnam from 2001 to 2006 were used to analyze the evolution of the hemagglutinin (HA), neuraminidase (NA), and matrix protein (M) genes. Phylogenetic analysis of individual gene segments revealed that the HA and the NA genes of the influenza A viruses evolved in a sequential way. However, the evolutionary pattern of the M gene proved to be nonlinear and was not linked with that of the HA and NA genes. Genetic drift in HA1 segments, especially in the antigenic sites of A/H3N2 viruses, occurred more frequently in A/H3N2 viruses than it did in A/H1N1 viruses. Two reassortants, one influenza A/H3N2 strain and one A/H1N1 strain, were found on the basis of the phylogenetic analysis of the three genes. While both genetic mutation and reassortment contributed to their evolution, the frequency of genetic changes and reassortment events differs between the two subtypes. As influenza viruses circulate throughout the year, we emphasize the importance of surveillance in tropical and subtropical zones, where the emergence of new strains may be detected earlier than it is in temperate zones.

* Corresponding author. Mailing address: Department of Public Health, Niigata University, Graduate School of Medical and Dental Sciences, 1-757, Asahimachi-Dori, Niigata City, Niigata Prefecture 951-8510, Japan. Phone: 81-25-227-2129. Fax: 81-25-227-0765. E-mail: bbmm{at}med.niigata-u.ac.jp

{triangledown} Published ahead of print on 17 October 2007.

Journal of Clinical Microbiology, February 2008, p. 399-405, Vol. 46, No. 2
0095-1137/08/$08.00+0     doi:10.1128/JCM.01549-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Furuse, Y., Suzuki, A., Kamigaki, T., Shimizu, M., Fuji, N., Oshitani, H. (2009). Reversion of Influenza A (H3N2) Virus from Amantadine Resistant to Amantadine Sensitive by Further Reassortment in Japan during the 2006-to-2007 Influenza Season. J. Clin. Microbiol. 47: 841-844 [Abstract] [Full Text]  
  • Suzuki, Y., Taira, K., Saito, R., Nidaira, M., Okano, S., Zaraket, H., Suzuki, H. (2009). Epidemiologic Study of Influenza Infection in Okinawa, Japan, from 2001 to 2007: Changing Patterns of Seasonality and Prevalence of Amantadine-Resistant Influenza A Virus. J. Clin. Microbiol. 47: 623-629 [Abstract] [Full Text]  


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