The sudden ability of the new swine flu virus to hop from pigs to humans and then to skip from person to person, at least in Mexico, is an excellent example of evolution at work.And why isn't there a cure for the flu? How come all we have to fight it are things like Tamiflu?:
"Yes, this is definitely evolution," said Michael Deem, a bioengineer at Rice University in Texas.
Deem studies how evolution is affected not just by mutations but by the exchange of entire genes and sets of genes. Viruses, which are basically packets of DNA with a protein coat, are really good at this. Viruses are also really good at exploiting the fact that we humans cough and sneeze without covering ourselves and generally don't wash our hands frequently in a day.
"Viruses have evolved to exploit human contact as a way of spreading," points out Peter Daszak of the Wildlife Trust, whose team 14 months ago predicted just this sort of evolution in an animal flu, coming from Latin America to the United States after evolving to infect people.
Let's say you have a run-of-the-mill flu that's normally transmitted between humans but causes only mild symptoms. Then you also contract a really deadly influenza virus that heretofore was only transmitted between pigs. The two viruses can get together inside you, swap genes, and now you're the host of a newly evolved swine flu virus that can infect your whole family, your colleagues at work, some people at the airport you later fly out of who touch the same armrest you held, and then some folks in the country you fly to. Voila, pandemic!
And it doesn't stop there. Each time another person is infected, the new strain of the virus can grab more genes and mutate further. So if you came from Mexico and infected people in the United States who might have been packing around a different flu, the U.S. swine flu could be different than the Mexican swine flu.
And that's why there's no cure for the flu.
Nasty stuff, that evolution.