LONDON (Reuters) -- Deaths and new cases of HIV/AIDS reached unprecedented highs in 2003 and are set to rise still further as the epidemic keeps a stranglehold on sub-Saharan Africa and advances across Eastern Europe and Central Asia.

New global estimates released Tuesday based on improved data show about 40 million people worldwide are living with HIV/AIDS, including an estimated 2.5 million children under 15 years old. About five million people were infected in 2003 and more than three million died.

"The AIDS epidemic continues to expand -- we haven't reached the limit yet," said Dr Peter Piot, head of the Joint United Nations Program on HIV/AIDS (UNAIDS). "More people have become infected this year than ever before and more people have died from AIDS than ever before," he told Reuters. "It is the first cause of death in Africa and the fourth cause of death worldwide." Burden OF Epidemic

Sub-Saharan Africa remains the worst affected region with about 3.2 million new infections and 2.3 million deaths in 2003. Southern Africa is home to about 30 percent of people living with HIV/AIDS, yet the region has less than two percent of the global population.

In Botswana and Swaziland the infection rate of HIV/AIDS among adults is 40 percent. One in five pregnant women in some African countries is infected with the virus, which is more easily transmitted from men to women than the other way around.

"In two short decades HIV/AIDS has tragically become the premier disease of mass destruction," Dr Jack Chow, of the World Health Organization (WHO) told a news conference. "The death odometer from HIV/AIDS is now at 8,000 a day and accelerating."

Piot said the epidemic, fueled by intravenous drug use and unsafe sex, is spreading in India, China, Indonesia, Papua New Guinea, Vietnam, the Russian Federation, Ukraine, Estonia and Latvia. And he predicted that it could be years before the back of the epidemic is broken in terms of new infections.

"The burden of the HIV epidemic will become bigger and bigger over time because it takes on average seven to 10 years after infection before you fall ill and, if there is no treatment, before you die," he said.