A study conducted by University of Oxford scientists of more than 2,000 women in Africa has revealed that the rapid evolution of the HIV virus is slowing its ability to cause AIDS, according to a Reuters report.

In the last decade, scientists say, the average time for an HIV infection to develop into AIDS has increased from 10 to 12.5 years in Botswana.

Once inside the body, HIV, a human immunodeficiency virus, attacks cells by entering them, copying itself and then multiplying rapidly before attacking new cells.

When the virus meets a strong immune system, however, it is forced to adapt over time and in order to survive it slows down its ability to replicate, and therefore in its ability to cause AIDS.

Scientists believe antiretroviral drugs are also forcing the virus to evolve into a milder form by preventing the virus from entering into cells or multiplying once inside the cell.

Scientists, however, warn that even a milder form of HIV can still be dangerous and eventually develop into AIDS.

Since HIV began its spread 30 years ago, AIDS has killed some 40 million people worldwide. Currently more than 35 million people are infected with HIV.