A new study shows that circumcision may stop millions of HIV deaths.

They analyzed data from trials that showed men who had been circumcised had a significantly lower risk of infection with the AIDS virus, and calculated that if all men were circumcised over the next 10 years, some two million new infections and around 300,000 deaths could be avoided.

Researchers believe circumcision helps cut infection risk because the foreskin is covered in cells the virus seems able to easily infect. The virus may also survive better in a warm, wet environment like that found beneath a foreskin.

So if men were circumcised, fewer would become infected and thus could not infect their female partners.

The human immunodeficiency virus or HIV, which causes AIDS, now infects close to 40 million people and has killed another 25 million. It mostly affects sub-Saharan Africa and the main mode of transmission is sex between a man and a woman.