Asia Is Traditional Cradle of Influenza because:

All flu viruses probably originate in birds, and the best environment for making the jump to humans is one where densely packed people live closely with birds and animals.

"In Asia we have a huge animal population, a huge bird population and two-thirds of the world's people living there," said Klaus Stohr, chief influenza scientist at the World Health Organization.

The population of China alone is bigger than that of the whole of Africa, and 80 percent of the new human flu strains the last few decades appeared in China first....

Asia's traditional situation of peasant farmers keeping ducks, chickens and pigs together with the family has long created opportunities for influenza to jump the species barrier.

And now industrial-scale commercial chicken farming is exacerbating the problem, said Robin Weiss, a professor of virology at University College in London....

Asians' fondness for shopping at live animal markets also adds to the chances for flu jumping species, experts say.

And climate may play a role. "Respiratory viruses, like orchids, do seem to like the Asian climate, because they have influenza viruses nearly all year round. It's not so seasonal as it is in the rest of the world," said John Oxford, a flu expert from Queen Mary School of Medicine in London.