The virus is becoming less deadly and less infectious, reports the University of Oxford.
The researchers showed that the virus is losing strength to adapt to our immune system and taking longer to cause AIDS
Some virologists suggest that the virus may become "almost harmless."
For researchers, the changes in the virus may help in efforts to contain the pandemic.
Today, HIV infects more than 30 million people in the world - in their bodies, there is a battle between the immune system and the virus. Like a master of disguise, the virus know quickly and with little effort undergo mutations to adapt to the immune system.
"[In these cases] the virus is between a rock and a sword," explains Professor Philip Goulder, of the University of Oxford. "It can lose effectiveness or become to survive and, if you have to change, it will cost."
The "cost" is a decrease in the ability to replicate, which causes the virus to become less infectious and take much longer to cause or even cause AIDS.
As this weakened virus is passed to others, begins a slow weakening cycle.
The team showed that process going on in Africa, comparing Botswana, where problems with HIV there a long time ago, and South Africa, where the virus came a decade later.
"It's amazing. You can see that the ability to replicate is 10% lower in Botswana than in South Africa, "Goulder told the BBC.
"We're seeing evolution happening in front of us and it is surprising how quickly the process is going on. The virus is losing its ability to cause disease and this will contribute to its elimination. "
The findings were published in the journal Proceedings of the National Academy of Sciences.
Of antiretroviral Attack
The study also suggests that antiretroviral drugs are forcing HIV to evolve into milder forms. The drugs would target mainly the more aggressive versions of HIV, allowing the playback of the less violent forms.
"Twenty years ago, AIDS manifested itself in ten years. But in the last ten years in Botswana, this may have increased to 12,5 years - a small increase, but that the general context is a quick change, "Goulder said.
"You can imagine that this extends more and that in the future, people can remain asymptomatic for decades."
"If the trend continues, then we can see a change in global scenario: a long illness being less transmissible," he told BBC Jonathan Ball, a virologist at the University of Nottingham.
"In theory, if we let HIV run its course, we would see the emergence of a stronger human population to the virus than we are today collectively. HIV infection would become almost harmless.
This probably happened throughout history, but we are talking about very large time scales. "
However, the group warned that even a weakened version of HIV is still dangerous and can cause AIDS.
Study showed that current capacity of the virus to replicate is less
Andrew Freedman, a specialist in infectious diseases at the University of Cardiff, called the study "intriguing".
"Researchers have been able to demonstrate how the virus is weakened over time. The widespread use of antiretroviral therapy may have a similar effect and contribute to the ultimate control of the HIV epidemic, "he said.
But he warned that HIV still has "a long way" to become harmless and that "other events can replace it, including broader access to treatment and eventually the development of a cure."
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