How The Flu Changes Within The Human Body.
An international team of scientists has determined the itinerary of the seasonal flu, paving the way for better monitoring and more effective vaccines. The researchers report in Science that they sussed out the bug’s travel plans by studying thousands of samples of the virus collected from every continent (except Antarctica) over the past years. Among their findings: seasonal flu originates in eastern and Southeast Asia. The result broadens previous hypotheses that such viruses emerged in China or exclusively in tropical regions. “For over 60 years the global travel patterns of the influenza virus have been a mystery,” study co-author Colin Russell, an epidemiologist specialising in pathogen evolution at the University of Cambridge in England said during a teleconference today. Russell said that he and his colleagues found that each year since 2002 new strains of influenza A (H3N2), the most infectious variety of seasonal flu, originated in “the east and Southeast Asian circulation network,” which spans from Malaysia and western Indonesia to Korea and Japan. The virus showed up in Europe and North America six to nine months later—and then continued on to South America. The finding will allow researchers to refine their search for new influenza strains and manufacture a yearly vaccine designed to give recipients resistance to the right ones. “Flu evolves quickly and in complex ways,” so this will help the World Health Organization (WHO) track and aim at the right strains with annual vaccines, says co-author Derek Smith, a Cambridge epidemiologist and member of the WHO committee tasked with planning WHO’s annual flu shot regimen. The researchers speculate that the broad range of climates in eastern Asia allows epidemics to arise in crowded areas at different times of the year. The flu typically strikes in temperate climes (like those in China) in winter months and in tropical areas, such as those in Vietnam, during their rainy seasons. “There is a lot of variability like this in east and Southeast Asia, so [there is] lots of opportunity for an epidemic in one country to seed an epidemic in another nearby country and then flow out of the region,” Smith says. Credit: Scientific American.
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