LONDON - Although millions have died in the thirty years since HIV/AIDS was first identified - and there will continue to be millions more infections - science has provided the means of keeping infected patients alive and symptom free, has discovered how to prevent infection, and has already begun to hold back the advance of the pandemic. Professor Richard Hayes of the London School of Hygiene & Tropical Medicine talks about recent achievements in the global battle against AIDS and explains why there are grounds for optimism.