Teaching Evolution

A blog devoted to teaching evolution, both in our schools and in our communities.

Thursday, September 29, 2005

Aids Virus Could be Weakening

This is so obvious I'm amazed I never thought of it before. It makes perfect sense that one of the reasons HIV has gone from a death sentence to a treatable illness is that the virus itself is weaker. We usually think of Darwinian evolution as the strong thriving while the weak die off, but think about what that means from the standpoint of a virus. If a virus is extremely strong, it will kill its host immediately -- before the host has had a chance to spread the virus to anyone else. And therefore the virus will be contained and will eventually die off, because it hasn't had the opportunity to find new hosts.

But a weak virus will stay around for a long time. If a virus takes decades to kill its host, it has decades to find new hosts.

As this article makes clear, newer samples of HIV appear not to multiply as well.

[Keith Alcorn, senior editor at the HIV information charity NAM, said] "This would suggest that over several generations, HIV could become less harmful to its human hosts.

"However, we are still far from that point - HIV is still a life-threatening infection."

Dr Marco Vitoria, an HIV expert at the World Health Organization, said other diseases - such as smallpox, TB and syphilis - had shown the same tendency to weaken over time.

"There is a natural trend to reach an 'equilibrium' between the agent and the host interests, in order to guarantee concomitant survival for a longer time," he said.

Note: Although I understand why it's necessary, I think it's a shame that writers of articles like this always feel the need to include so many disclaimers that "the latest findings should not lull people into a false sense of security." Only an idiot would come across this article and conclude that AIDS is no longer anything to worry about. I guess there are enough idiots out there, though, that it's a point that needs to be stressed.

Hat tip: Andrew Sullivan

UPDATE: An interesting look at the evolution of the cholera virus here.


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