Viral Time: Carl Zimmer's talk at the Long Now Foundation

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This is a talk I gave on June 7, 2011 at the Long Now Foundation in San Francisco. It's based mainly on my book, A Planet of Viruses (University of Chicago Press, 2011) The audio is available here: http://blogs.discovermagazine.com/loom/2011/06/09/my-long-now-lecture-viral-time-slides-and-audio/

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  • But you don’t read about viruses, or any other disease-causing microbe. There’s a great irony in that, and one that I’m going to explore tonight. Because, 150 years after the Origin of Species came out, there’s no better demonstration of the power of Darwin’s ideas than swine flu.\n
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  • Now, let’s go back to the Origin of Species and think about what it means for the flu.\n\nAmong Darwin’s great insights was that all living things are related to other living things. Species are cousins. He envisioned the process like the branching of a tree. \n
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  • I fully expect that in five years, this talk will look incredibly quaint. It’s hard to guess where things will go.\n
  • \nA woman, wearing a face mask as a precaution against swine flu, holds a skeletal figure representing the folk saint known in Mexico as Santa Muerte, or Death Saint, during a ceremony in Mexico City, Friday May 1, 2009. (AP Photo/Eduardo Verdugo)\n
  • Another way to make new virus genomes: sex. Two enter cell at once, make genes, genes incorrectly sorted. Turns out to happen a lot more than people thought. With all the different strains circulating, lots of opportunity for one person to come down with two substrains. \n
  • Big explanation of diversity process. Then...step back: big picture. where does flu come from? where do pandemics start?\n\n\nBlue and yellow viruses depict two antigenically similar strains of the same subtype circulating in the human population. The genetic diversity of the circulating viral population increases through mutation and reasssortment. Single white arrows indicate relationships between ancestral and descendant viruses. White marks on the segments indicate neutral mutations and red marks indicate mutations that affect the antigenic regions of the surface proteins. Incoming pairs of orange arrows indicate the generation of reassortants with segments from two different ancestral viruses. As these viruses continue to circulate, immunity against them builds up in the host population, represented here by the narrowing of the bottleneck. In parallel, viruses with mutations affecting the antigenic regions of the surface proteins accumulate in the viral population. At some point a novel antigenic drift variant, indicated by a red colored virus, which is less affected by immunity in the human population, is generated. This variant is able to cause widespread infection and founds a new cluster of antigenically similar strains.\n
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  • Note: 1918, classical swine: over 60, some protection when still around in 1940s . Everything went into pigs. Worobey: 1.5 times faster in humans. Adapting to us. \nPigs have receptors for bird flu, and other receptors for human flu. So they can be a mixing vessel for reassortment.\n
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  • Also revealed where we got this new flu from. Not directly from birds. But from pigs. To understand this, a little background. Spanish flu--simultaneous with flu in pigs. Looks like pigs got it from us, or maybe from the same birds. Not clear. But in any case, pigs become hosts to flu viruses ever since.\n
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  • On top of the seasonal patterns of flu, there are other patterns. Every now and then flu gets out of control. Way out of control. These global spikes of flu are known as pandemics. In 1918, a pandemic swept through the world.\n
  • Billions of people may have become infected, and of them, only a small percentage died. But that was enough to kill perhaps 50 million people.\n
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