These findings suggest that by focusing surveillance efforts on East and Southeast Asia, researchers may be able to extend their forecast of the flu strains most likely to cause epidemics, which may in turn help experts decide which strains should go in the flu vaccine each year.
The study, by a team of researchers from Europe, Australia, Japan and the United States, appears in the 18 April issue of the journal Science, which is published by AAAS, the nonprofit science society.
“The flu virus is constantly mutating, so it’s a major challenge for public health as well as a fascinating example of evolution in action. This study advances our knowledge of how new flu strains spread across the globe and how epidemics arise,” said Katrina Kelner, Science’s deputy managing editor, life sciences.
Colin Russell of the University of Cambridge in the United Kingdom and his colleagues analyzed 13,000 samples of influenza A (H3N2) virus, collected across six continents from 2002 to 2007 by the World Health Organization Global Influenza Surveillance Network. This subtype of influenza is currently the major cause of flu-related illness and death in humans.
The researchers compared physical differences in a surface protein, called hemagglutinin, across the different samples. Hemagglutinin is the primary target of the immune response, and even small changes can allow the virus to evade the immune system and cause disease.
In a subset of the samples, the researchers also compared the sequences of the gene that codes for hemagglutinin.
Together, these analyses allowed the researchers to identify different strains of A (H3N2) as they arrived at new locations around the world over the five-year period. The results revealed that strains emerge in East and Southeast Asia and then about six to nine months later reach Europe and North America. Several months later still, the strains arrive in South America. Essentially, once the strains leave East and Southeast Asia they enter an evolutionary graveyard.
“The ultimate goal of our collaboration is to increase our ability to predict the evolution of influenza viruses. This study is one step along that path and in particular highlights the importance of ongoing collaborations and surveillance in East and Southeast Asia, and of expanding these collaborations in the future,” said Derek Smith of the University of Cambridge, who is the corresponding author of the study.
Annual influenza epidemics are thought to result in 3 to 5 million cases of severe illness, and between 250,000 and 500,000 deaths every year, according to the World Health Organization (http://www.who.int/mediacentre/factsheets/fs211/en/index.html).
A (H3N2) is a subtype of the influenza A virus, and it is one of the three flu viruses included – in dead or in a weakened state – in the flu vaccine. The others are the influenza A (H1N1) subtype and the influenza B virus. Each year, the World Health Organization decides which strains within these three categories to include in the next vaccine, based on the recent activity of strains that are currently circulation.
The authors emphasized that the flu vaccine currently works extremely well, protecting about 300 million people from the disease each year, and that people should continue to be vaccinated annually. But, from time to time, a new strain begins infecting people after the vaccine has already been produced.
For decades, researchers haven’t known how influenza viruses migrate around the world. According to some of the scenarios that have been proposed, the viruses may migrate between the Northern and Southern hemispheres following the seasons, or they may have come out of the tropics where they were thought to circulate continuously, or they may have come out of China.
The Science study shows instead that each year since 2002, influenza A (H3N2) viruses have migrated out of what the authors call the “East and Southeast Asian circulation network,” and from there spread around the world.
Why Asia" For reasons that aren’t well-understood, flu epidemics break out during the rainy seasons in the tropics of East and Southeast Asia. On continents at higher latitudes, on the other hand, flu season simply occurs for a few months during the wintertime. Within Asia, different regions experience the rainy season at different times of year.
“Flu epidemics appear to be driven by seasonal factors such as winter, or rainy seasons. So there can be cities that are only 700 miles away from each other, such as Bangkok and Kuala Lumpur, which have epidemics six months apart. There is a lot of variability like this in East and Southeast Asia, so lots of opportunity for an epidemic in one country to seed an epidemic to another nearby country, like a baton passed by runners in a relay race,” Smith said.
“Our study is an example of the tremendous synergy between influenza science and public health,” he said. “The World Health Organization’s Global Influenza Surveillance Network tracks the evolution of influenza viruses for the primary purpose of influenza vaccine strain selection, but this also enables basic work on evolution.”
"The Global Circulation of Seasonal Influenza A (H3N2) Viruses," by C.A. Russell; T.C. Jones; A, Mosterin; E. Skepner; D.J. Smith at University of Cambridge in Cambridge, UK; T.C. Jones; J.C. de Jong; A.D.M.E. Osterhaus; G.F. Rimmelzwaan; R.A.M. Fouchier; D.J. Smith at Erasmus Medical Centre in Rotterdam, Netherlands; T.C. Jones; A. Mosterin at Universitat Pompeu Fabra in Barcelona, Spain; I.G. Barr; N.J. Cox; R.J. Garten; V. Gregory; I.D. Gust; A.W. Hampson; A.J. Hay; A.C. Hurt; A. Kelso; A.I. Klimov; T. Kageyama; N. Komadina; Y.P. Lin; M. Obuchi; T. Odagiri; M.W. Shaw; M. Tashiro at World Health Organization (WHO) Collaborating Centre for Reference and Research on Influenza in Melbourne, VIC, Australia; N.J. Cox; R.J. Garten; A.I. Kilmov; M.W. Shaw at Centers for Disease Control and Prevention in Atlanta, GA; V. Gregory; A.J. Hay; Y.P. Lin at National Institute for Medical Research in London, UK; T. Kageyama; M. Obuchi; T. Odagiri; M. Tashiro at National Institute for Infectious Diseases in Tokyo, Japan; A.S. Lapedes at Los Alamos National Laboratory in Los Alamos, NM; K. Stohr at Novartis Vaccines and Diagnostics in Boston, MA.
This study was funded by the National Institutes of Health Director’s Pioneer Award (http://nihroadmap.nih.gov/pioneer), the National Institute of Allergy and Infectious Diseases, the NWO Netherlands Influenza Vaccine Research Centre, the Australian Government Department of Health and Aging, and the Medical Research Council.
The American Association for the Advancement of Science (AAAS) is the world's largest general scientific society, and publisher of the journal Science (www.sciencemag.org). AAAS was founded in 1848, and serves 262 affiliated societies and academies of science, reaching 10 million individuals. Science has the largest paid circulation of any peer-reviewed general science journal in the world, with an estimated total readership of 1 million. The nonprofit AAAS (www.aaas.org) is open to all and fulfills its mission to "advance science and serve society" through initiatives in science policy; international programs; science education; and more. For the latest research news, log onto EurekAlert!, www.eurekalert.org, the premier science-news Web site, a service of AAAS.
Natasha Pinol | EurekAlert!
Study suggests possible new target for treating and preventing Alzheimer's
02.12.2016 | Oregon Health & Science University
The first analysis of Ewing's sarcoma methyloma opens doors to new treatments
01.12.2016 | IDIBELL-Bellvitge Biomedical Research Institute
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy