New study: HIV evolving 'into milder form'

[natasa778]

http://www.bbc.co.uk/news/health-30254697

every so often HIV infects someone with a particularly effective immune system.
"[Then] the virus is trapped between a rock and hard place, it can get flattened or make a change to survive and if it has to change then it will come with a cost," said Prof Philip Goulder, from the University of Oxford.

The "cost" is a reduced ability to replicate, which in turn makes the virus less infectious and means it takes longer to cause Aids.

This weakened virus is then spread to other people and a slow cycle of "watering-down" HIV begins.

The team showed this process happening in Africa by comparing Botswana, which has had an HIV problem for a long time, and South Africa where HIV arrived a decade later.

Prof Goulder told the BBC News website: "It is quite striking. You can see the ability to replicate is 10% lower in Botswana than South Africa and that's quite exciting.

"We are observing evolution happening in front of us and it is surprising how quickly the process is happening. ...

 

[barbc56]

The findings in Proceedings of the National Academy of Sciences also suggested anti-retroviral drugs were forcing HIV to evolve into milder forms.

It showed the drugs would primarily target the nastiest versions of HIV and encourage the milder ones to thrive.

Prof Goulder added: "Twenty years ago the time to Aids was 10 years, but in the last 10 years in Botswana that might have increased to 12.5 years, a sort of incremental change, but in the big picture that is a rapid change

Interesting. I wonder which factor is more likely to do this?

Thanks

Barb
.

 

[Hip]

A similar thing happened to syphilis: it became milder over time.

When syphilis first appeared in Naples in the 15th century (it was probably imported from the New World), this pathogen was far more deadly and downright awful than the syphilis we know today. When it first appeared, syphilis was so virulent that it killed within months, and there were gruesome descriptions of the flesh literally falling off the bodies of those with syphilis infections!

However pathogens are subject to evolutionary forces, which can change their virulence level over time. Evolutionary biologist Paul Ewald talks about how, depending on the circumstances, if a pathogen evolves to become more virulent and to kill more quickly, that pathogen can sometimes have less chances of transmission into new hosts (which is fundamental for its survival) compared to if it evolves into a milder, less virulent version. Milder versions of pathogens can have greater chances of survival because if their host lives longer, there can be more opportunities for that host to come into contact with and spreading the infection to new hosts.

Crowded environments such as cities, where there are numerous opportunities to come into contact with potential new hosts, tend to favor evolution towards milder versions of pathogens.

 

[natasa778]

Crowded environments such as cities, where there are numerous opportunities to come into contact with potential new hosts, tend to favor evolution towards milder versions of pathogens.

Yes, but that is usually believed to happen over longer periods of time. What is new in this case is that seems to be happening at a rapid speed. Or at least this is the first time such a rapid transformation has been observed

 

[Hip]

@natasa778
True, although the article said that there was only a small 10% reduction in the ability to replicate. Presumably this reduction has occurred over the last 25 - 30 years, in the time since HIV was first discovered in the 1980s.

I am not sure how quickly syphilis took to evolve to a more benign form.