Sub-Saharan Africa: Almost three-quarters of deaths from AIDS in 2006 occurred there and two-thirds of those living with HIV are in that area
UNAids says there are an estimated 39.5 million people now living with HIV.
The number living with the virus has increased everywhere, with the most striking increases in East Asia and Central Asia/Eastern Europe.
Some countries, such as Uganda, are seeing a resurgence in new HIV infection rates which were previously stable or declining.
The report, which is based on disease surveillance around the world, says there were an estimated 4.3 million new HIV infections this year, with 2.8 million of these occurring in sub-Saharan Africa.
Forty per cent of new infections were in people aged 15 to 24-years-old.
In 2006, 2.9 million died of Aids-related illnesses.
The report says: "The future course of the world's HIV epidemics hinges in many respects on the behaviours young people adopt and maintain, and the factors that affect those choices."
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