The Global Circulation of Seasonal Influenza A (H3N2) Viruses

Department of Zoology, University of Cambridge, Cambridge, UK.
Science (Impact Factor: 33.61). 05/2008; 320(5874):340-6. DOI: 10.1126/science.1154137
Source: PubMed


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, Oct 13, 2015
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    • "Influenza A virus infection is a major global health challenge [1,2]. Although the virus infects people of all ages, elderly individuals (>75 years old) have more than 10-fold higher influenza-associated hospitalization and higher mortality compared to other age groups [3]. "
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    ABSTRACT: Background Influenza virus infection causes significantly higher levels of morbidity and mortality in the elderly. Studies have shown that impaired immunity in the elderly contributes to the increased susceptibility to influenza virus infection, however, how aging affects the lung tissue damage and repair has not been completely elucidated.Methods Aged (16¿18 months old) and young (2¿3 months old) mice were infected with influenza virus intratracheally. Body weight and mortality were monitored. Different days after infection, lung sections were stained to estimate the overall lung tissue damage and for club cells, pro-SPC+ bronchiolar epithelial cells, alveolar type I and II cells to quantify their frequencies using automated image analysis algorithms.ResultsFollowing influenza infection, aged mice lose more weight and die from otherwise sub-lethal influenza infection in young mice. Although there is no difference in damage and regeneration of club cells between the young and the aged mice, damage to alveolar type I and II cells (AT1s and AT2s) is exacerbated, and regeneration of AT2s and their precursors (pro-SPC-positive bronchiolar epithelial cells) is significantly delayed in the aged mice. We further show that oseltamivir treatment reduces virus load and lung damage, and promotes pulmonary recovery from infection in the aged mice.Conclusions These findings show that aging increases susceptibility of the distal lung epithelium to influenza infection and delays the emergence of pro-SPC positive progenitor cells during the repair process. Our findings also shed light on possible approaches to enhance the clinical management of severe influenza pneumonia in the elderly.
    Respiratory Research 09/2014; 15(1):116. DOI:10.1186/PREACCEPT-1989848861132152 · 3.09 Impact Factor
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    • "China is home to over one-seventh of the world's population and is part of a region thought to play a critical role in global influenza dynamics [18]. Southern China has a high population density, is highly connected to regional and global population centres in terms of human and animal transportation and has been implicated in the emergence of SARS and H5N1 avian influenza [19,20]. "
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    ABSTRACT: A dense population, global connectivity and frequent human-animal interaction give southern China an important role in the spread and emergence of infectious disease. However, patterns of person-to-person contact relevant to the spread of directly transmitted infections such as influenza remain poorly quantified in the region. We conducted a household-based survey of travel and contact patterns among urban and rural populations of Guangdong, China. We measured the character and distance from home of social encounters made by 1821 individuals. Most individuals reported 5-10 h of contact with around 10 individuals each day; however, both distributions have long tails. The distribution of distance from home at which contacts were made is similar: most were within a kilometre of the participant's home, while some occurred further than 500 km away. Compared with younger individuals, older individuals made fewer contacts which tended to be closer to home. There was strong assortativity in age-based contact rates. We found no difference between the total number or duration of contacts between urban and rural participants, but urban participants tended to make contacts closer to home. These results can improve mathematical models of infectious disease emergence, spread and control in southern China and throughout the region.
    Proceedings of the Royal Society B: Biological Sciences 04/2014; 281(1785):20140268. DOI:10.1098/rspb.2014.0268 · 5.05 Impact Factor
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    • "In addition to the above-mentioned evidence for the scenario ― a new viral variant emerged from East and Southeast Asia (E-SE Asia) during the 2009 season ― several studies have shown that seasonal influenza epidemics are usually seeded from E-SE Asia or China [12,13]. Fluctrl thus provides a functionality for limiting the scope of analyzed human influenza data to E-SE Asia by constraining the latitude (between −8 and 8) and the longitude (between 70 and 150) that were extracted from strain information. "
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    ABSTRACT: Background The World Health Organization (WHO) organizes consultations in February and September of each year, spearheaded by an advisory group of experts to analyze influenza surveillance data generated by the WHO Global Influenza Surveillance and Response System (GISRS). The purpose of these consultations is to recommend the composition on influenza virus vaccines for the northern and southern hemispheres, respectively. The latest news of influenza viruses is made available to the public and updated on the WHO website. Although WHO discloses the manner in which it has made the recommendation, usually by considering epidemiological and clinical information to analyze the antigenic and genetic characteristics of seasonal influenza viruses, most individuals do not possess an understanding of antigenic drift and when it occurs. Findings We have constructed a web server, named Fluctrl, and implemented a pipeline whereby HA sequence data is downloaded from the Influenza Virus Resource at NCBI along with their isolation information including isolation year and location, which are parsed and managed in MySQL database. By analyzing the frequency of each amino acid residue of the HA1 domain expressed by the viruses on annual basis, users are able to obtain evolutionary dynamics of human influenza viruses corresponding with epidemics. Users are able to upload and analyze their HA1 sequences for generating evolutionary dynamics. In addition, a distribution of amino acid residues at a particular site is represented geographically to trace the location where antigenic variants are seeded. Conclusions Fluctrl is constructed for monitoring the antigenic evolution of human influenza A viruses. This tool is intended to inform the general public how and when influenza viruses evade the human body's immunity. Furthermore, leveraging the geographic information, the original locations of emerging influenza viruses can be traced. Fluctrl is freely accessible at
    BMC Research Notes 06/2013; 6(1):227. DOI:10.1186/1756-0500-6-227
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