What benefit does HIV derive from being such a lethal virus (without treatment, that is)?

Evolutionarily, this makes no sense. One would expect it to be pretty latent and harmless so it could infect the most people and spread its genome.

Good question actually. According to theory, viruses should evolve to a point where they reach their maximum reproductive rate without harming their host. But obviously there are many exceptions to the rule.

So let's look at HIV for example. HIV is limited to infecting T-cells, a critical component of the immune system. Obviously if you replicate too fast you will kill your host cell, and if you and your fellow viruses kill too many cells you will kill your host. So logically you should be evolving forms of the virus that don't kill the host cell right?

But here's the problem, if you make that mutation and become a milder form of the virus you can't compete with the other HIV populations from other cells, and you are an evolutionary dead end. The reality is that every virus has to balance the need to keep their host alive with the need to be the best replicating virus in the host.

HIV ends up doing a smashing job of this, by establishing an infection that does not affect the overall health of the host for years. In addtion, HIV is transmitted easily by a high density host population, further encouraging the damaging (virulent) forms of the virus. The HIV infection rates are good evidence that this is a very successful virus.

it does ......its survival of fittest it multiplies in human or monkeys deriving there nutrition from them in turn growing n spreading from one being to another ..........thats what evolution means growth and if it is not in balance wt nature it will get wiped out ....hiv is a virus which is harmless but it thrives on human defence mechanisam in turn turning the host harbouring the visus defenceless against those infectious bacteria or virus which could hv been eliminated wt the help of a defence mechanism in body....... some things look harmless but harm indirectly

HIV show signs of mutating very rapidly.

There are some people whose immune systems are able to keep the HIV vius from turning to full blown AIDS. In these cases one could say that the parasitic virus is behaving in an optimal manner.

In those cases where it eventually kills it's host it does not do so until after a long time period has elapsed giving the virus plenty of time to pass on it's offspring to others. So there does not appear to be little evolutionary penalty to killing the host.

Eventually one could imagine after several thousand years if we didn't find a cure that everyone would be HIV positive but that people whose immune systems who can coexist with the virus would be the only ones left. The people who couldn't would die off gradually producing less offspring until there were none left. Not a realistic scenario though since our medical knowledge is growing much faster than the evolutionary timeframe.

must be asexual.

It actually started out as an infectious virus in chimpanzees, called SIV, or Simian Immunodeficiency Virus. So in that form it was not as deadly, and was very good at just being a virus. When it got contracted from man eating bushmeat, or chimpanzee meat, it became a much more deadly virus, and now it does not make sense how fast it kills, yet it still does. But you must understand that it gets spread still, and the reason is that people do not know they have it, and spread it before they find out, so it must be doing something right, evolutionarily...

I love the explanations that treat the retrovirus as if it was a higher order thinking organism. Retroviruses have one purpose - too multiply. HIV replicates by attaching to CD-4 lymphocytic cells (T-cell), inserting its DNA, and rewriting the T-cell's RNA to produce copies of itself. This is its sole purpose. The reason it is lethal is that the CD-4 Lymphocytic cells in the human body are a critical component of the human immune system. As the virus replicates, it reduces CD-4 counts in the human system.

Think of the infected human system as a control environment. The HIV retrovirus must either replicate or die within this closed system. Within the closed system, the retrovirus has shown that it can evolve. As individuals stay on medical therapies for extended periods of time, the virus mutates in order to survive the effects of a particular medication. When this happens, the individual must change treatments. It is a cycle of mutation that is only staved off by the speed in which pharmaceutical research can provide new formulations of medications.

The HIV retrovirus is not planning world domination, but simply striving to best perform its base function within the closed system it finds itself in.

Todd (AIDS - positive since 2004)

P.S. - Sammyboy, are you ever going to contribute anything other than that dangerous propaganda about HIV and AIDS?