The global circulation of seasonal influenza A (H3N2) viruses.

Department of Zoology, University of Cambridge, Cambridge, UK.
Science (Impact Factor: 31.48). 05/2008; 320(5874):340-6. DOI: 10.1126/science.1154137
Source: PubMed

ABSTRACT Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection.

Download full-text


Available from: Masato Tashiro, Jun 28, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We describe a multiple strain Susceptible Infected Recovered deterministic model for the spread of an influenza subtype within a population. The model incorporates appearance of new strains due to antigenic drift, and partial immunity to reinfection with related circulating strains. It also includes optional seasonal forcing of the transmission rate of the virus, which allows for comparison between temperate zones and the tropics. Our model is capable of reproducing observed qualitative patterns such as the overall annual outbreaks in the temperate region, a reduced magnitude and an increased frequency of outbreaks in the tropics, and the herald wave phenomenon. Our approach to modelling antigenic drift is novel and further modifications of this model may help improve the understanding of complex influenza dynamics. AMS Subject Classification: 92D30; 92D15
    Journal of Biological Dynamics 05/2013; 7(1). DOI:10.1080/17513758.2013.801523
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bangladesh has been severely hit by highly pathogenic avian influenza H5N1 (HPAI-H5N1). However, little is known about the genetic diversity and the evolution of the circulating viruses in Bangladesh. In the present study, we analyzed the hemagglutinin gene of 30 Bangladeshi chicken isolates from 2007 through 2010. We analyzed the polybasic amino acid sequence motif of the cleavage site and amino acid substitution pattern. Phylogenetic history was reconstructed using neighbor-joining and Bayesian time-scaled methods. In addition, we used Mantel correlation tests to analyze the relation between genetic relatedness and spatial and temporal distances. Neighbor-joining phylogeography revealed that virus circulating in Bangladesh from 2007 through 2010 belonged to clade 2.2. The results suggest that clade 2.2 viruses are firmly entrenched and have probably become endemic in Bangladesh. We detected several amino acid substitutions, but they are not indicative of adaptation toward human infection. The Mantel correlation test confirmed significant correlation between genetic distances and temporal distances between the viruses. The Bayesian tree shows that isolates from waves 3 and 4 derived from a subgroup of isolates from the previous waves grouping with a high posterior probability (pp=1.0). This indicates the possibility of formation of local subclades. One surprising finding of spatio-temporal analysis was that genetically identical virus caused independent outbreaks over a distance of more than 200km and within 14 days of each other. This might indicate long distance dispersal through vectors such as migratory birds and vehicles, and challenges the effectiveness of movement restriction around 10km radius of an outbreak. The study indicates possible endemicity of the clade 2.2 HPAI-H5N1 virus in Bangladesh. Furthermore, the formation of a subclade capable of transmission to humans cannot be ruled out. The findings of this study might provide valuable information for future surveillance, prevention and control programme.
    Vaccine 10/2012; 30(51). DOI:10.1016/j.vaccine.2012.09.081 · 3.49 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Swine have often been considered as a mixing vessel for different influenza strains. In order to assess their role in more detail, we undertook a retrospective sequencing study to detect and characterize the reassortants present in European swine and to estimate the rate of reassortment between H1N1, H1N2 and H3N2 subtypes with Eurasian (avian-like) internal protein-coding segments. We analysed 69 newly obtained whole genome sequences of subtypes H1N1-H3N2 from swine influenza viruses sampled between 1982 and 2008, using Illumina and 454 platforms. Analyses of these genomes, together with previously published genomes, revealed a large monophyletic clade of Eurasian swine-lineage polymerase segments containing H1N1, H1N2 and H3N2 subtypes. We subsequently examined reassortments between the haemagglutinin and neuraminidase segments and estimated the reassortment rates between lineages using a recently developed evolutionary analysis method. High rates of reassortment between H1N2 and H1N1 Eurasian swine lineages were detected in European strains, with an average of one reassortment every 2-3 years. This rapid reassortment results from co-circulating lineages in swine, and in consequence we should expect further reassortments between currently circulating swine strains and the recent swine-origin H1N1v pandemic strain.
    Journal of General Virology 09/2012; 93(Pt Pt_11):2326-2336. DOI:10.1099/vir.0.044503-0 · 3.53 Impact Factor