CR says the notion that the flu virus originates in Asia isn't new but hadn't been proven and others hypotheses had been discussed, such as the virus moving between the hemispheres following the seasons. (So how did you narrow down the origins?) We analyzed about 13,000 season flu viruses of the H2N5 subtype and we were able to trace the origins to East Asia. (Does it build on previous flu forms? How does it even start?) Flu viruses circulate continuously from East to Southeast Asia, like runners passing a tong in a relay race. So the viruses are constantly evolving in Asia and then spread out to the rest of the world and then epidemics take off when the climatic factors are appropriate. (What kind of climatic factors?) Well flu is a winter virus. So if viruses come in the summer, they don't normally cause an epidemic. DS: In the tropics, it's different. The influenza epidemics look like they're associated with rainy seasons. (So what you've been able to do is narrow the origins of the flu but also how it migrates. Tell us about this new computation technique called antigenic cartography that you used.) DS: AC is a way of taking the phenotypic data about viruses and increasing the resolution of that data. Phenotypic data is how the virus looks to the immune system. This allowed us to take this global data set and increase the resolution at which the data could be analyzed and do statistical analyses to find the origins. (do people still die from the flu?) about half a million around the world every year and 5-15% of the world's population gets the flu every year.

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