Researchers at Duke- National University of Singapore Graduate Medical School have found that influenza virus in tropical areas isn’t the only global source of flu epidemics.
The international team of scientists involved in the work found that any one of the urban centers they studied could act as a source for a flu epidemic in any other locality.
The study was published in the online Early Edition of the Proceedings of the National Academy of Sciences.
“We found that these regions are just one node in a network of urban centers connected by air travel, through which flu virus circulates and causes a series of local epidemics that overlap in time,” said Gavin Smith, PhD, senior author and Associate Professor in the Program in Emerging Infectious Diseases at Duke-NUS.
The team obtained RNA sequences of virus samples from 2003 to 2006 in Australia, Europe, Japan, New York, New Zealand and Southeast Asia, as well as some more recently sequenced viruses from Hong Kong. The virus populations from tropical Southeast Asia and Hong Kong showed relatively low levels of genetic diversity and no seasonal fluctuations in comparison with temperate-area epidemics.
The analysis used time and space parameters to reveal high rates of viral migration among the urban centers tested.
Many examples of the global movement of viruses facilitated by air travel exist, including the SARS epidemic and the H1N1 pandemic in 2009, Smith said. “Larger regions with greater connectedness may potentially contribute more to the global diversity of influenza viruses circulating.”
Other authors were from Department of Microbiology, State Key Laboratory of Emerging Infectious Diseases, Department of Community Medicine and School of Public Health, Li Ka Shing Faculty of Medicine, and Hong Kong University-Pasteur Research Centre, University of Hong Kong, Pokfulam, in the Hong Kong Special Administrative Region; Laboratory of Virus Evolution, Program in Emerging Infectious Diseases, Duke–National University of Singapore Graduate Medical School; Fogarty International Center, National Institutes of Health, Bethesda, Md.; University of Texas Medical Branch, Galveston; J. Craig Venter Institute, Rockville, Md.; Center for Vaccine Research, Department of Computational and Systems Biology, University of Pittsburgh School of Medicine; Medical Research Council Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College, London; Institute of Evolutionary Biology, University of Edinburgh; and the Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University.
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