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.

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Available from: Masato Tashiro, Aug 19, 2015
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    • "We illustrated that, with suitable parameter values, the same model is capable of capturing the observed influenza patterns in both temperate and tropical regions. Our simulation results suggest that the seasonal variation might be responsible for observed patterns in influenza including: (i) higher frequency of disease recurrence in tropical regions than in the temperate regions (annual); (ii) reduced magnitude of disease outbreaks in tropical regions than in temperate regions [1] [15] [21]; and (iii) annual peaks during winter in temperate regions that are interspersed by bottlenecks of emerging strains during summer months [20]. Since our model does not take into account other very important factors that can influence seasonality as discussed in Section 2.3, it cannot predict what would happen in a particular region. "
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