Seasonal Flu Outbreaks Start in Asia: Study

Steven Reinberg, HealthDay Reporter

Each year, new strains of virus that produce seasonal flu epidemics start in East Asia and Southeast Asia and then spread around rest of the world, researchers report.

And by focusing on new flu strains emerging in Asia, scientists may be able to improve their forecast of seasonal flu strains and develop better vaccines, the researchers said.

"For over 60 years, the global migration pattern of influenza has been a mystery," lead researcher Colin Russell, of the University of Cambridge in England, said during a Wednesday teleconference.

Conventional wisdom has held that flu viruses migrate between the northern and southern hemispheres after the flu season. Other theories contend that the viruses surface in the tropics and circulate continuously, or start out in China, Russell said.

"We found solid evidence that influenza H3N2 viruses [the most common viruses] have migrated out of what we call the East and Southeast Asian circulation ...