This will be my last flu-related post for now, unless everything unexpectedly gets out of hand. But now that we’re not panicking any longer, perhaps it might be time to look into how the H1N1 virus came about. The best description comes from Carl Zimmer (author of the blog The Loom and our 2005 story on life on Mars), writing in Tuesday’s New York Times, and I encourage you to read the entire article. But the following passage struck me because I had run across an animation last week that illustrated exactly what Zimmer was describing:
Viruses are diverse because they can mutate very fast and can mix genes. They sometimes pick up genes from their hosts, and they can swap genes with other viruses. Some viruses, including flu viruses, carry out a kind of mixing known as reassortment. If two different flu viruses infect the same cell, the new copies of their genes get jumbled up as new viruses are assembled.
This is called “antigenic shift”: