Tuesday, 2 December 2014

Not a surprise at all, but a pleasant one nonetheless.

From the BBC:

HIV is evolving to become less deadly and less infectious, according to a major scientific study. The team at the University of Oxford shows the virus is being "watered down" as it adapts to our immune systems.

It said it was taking longer for HIV infection to cause Aids and that the changes in the virus may help efforts to contain the pandemic. Some virologists suggest the virus may eventually become "almost harmless" as it continues to evolve.

This is something else covered in "Guns, Germs and Steel". We have observed similar things happening with many other infectious diseases for example syphilis.

Basically, germs want to maximise their own number. So the ideal outcome is for their hosts to remain alive but infectious.

There is no mileage in killing off your host; germs like it when their hosts produce and discharge more germs to infect others (coughing, sneezing, vomiting and other things too disgusting to mention on a family blog). The unfortunate side-effect of this, from the germs' point of view, is that they overdo it and the symptoms kill their hosts (who can no longer infect others) and thereby some of their own number.

The side effect of becoming less lethal is that they become less infectious as well; there's simply not the hurry. If you are a disease that kills within a couple of days, each host has to infect at least one other host in the next couple of days. If you are a slow-killer or non-killer disease, you can take your time, if your host only infects one new host every few years, then that is enough.

Diseases which kill nearly everybody they infect soon disappear because they run out of victims; either they are dead or immune (by luck or acquired). We see the same thing happening with Ebola, there's a nasty outbreak every decade or two, then it all quietens down again.

See also: why animals on isolated islands tend towards vegetarianism.


ageing man said...

I read that article but when I read the last para...."But he cautioned HIV was "an awfully long way" from becoming harmless and "other events will supersede that including wider access to treatment and eventually the development of a cure"..... I was somewhat left thinking.... and your point of the article?

It did have the whiff of typical BBC science stories of ..... "one step closer to Harry Potter invisibility cloak"..... only to then read about the theory of possibly wobbling light around an atom, on paper, using computer modelling projecting outcomes for the year 2034.

Last night BBC1 answered all our "fears' about Ebola in a 30 minute in depth idiots guide to Ebola. I can only imagine some little old deary is today discarding her life time of condoms, knowing she is safe to shag her self senseless before Ebola gets her, now confident that HIV is off the menu....

Sometimes I think the BBC should come with it's own health warning...

Ben Jamin' said...

"The side effect of becoming less lethal is that they become less infectious as well; there's simply not the hurry."

As you said, it's the incubation period that really matters with lethal viruses.

What i find interesting is how viruses evolve and survive by changing the behavior of their host.

Syphilis and toxoplasma being two examples.

Lola said...

So that's it for Zombies then.

Mark Wadsworth said...

AM, it's a long way from becoming "harmless" but it is less harmful than it was.

BJ, the symptoms are partly the germs' way of getting you to spread them, such as sneezing.

L, zombies? That's a made up disease.

Anonymous said...

Ben Jamin'; I recall hearing about one particular parasite nematode whose precise name escapes me, which basically get's itself into the nervous system of an ant by being eaten. The larvae hatch inside the ants when they are fed by adult ants whilst still in the larvae stage and when the ant gets bigger it's belly turns bright red. It makes the ant project it's abdomen in such a way as to be more visible from above, so tempting birds who don't eat ants but think the bright red abdomen may be a berry, who then eat it, excrete it whereupon it's quite appealing to...ants, who feed it to their young.

Robin Smith said...

True. HIV was a very unsuccessful virus if it destroys all its 'land value'.

Somewhat like rent caps to cure low wages.

But there's more: AIDS is a myth don't you know?


Stop believing what you read in the papers - The Olds