Within the next 25 years, AIDS is set to join heart disease and stroke as the top three causes of death worldwide, with estimates that at least 117 million people will die from the disease by 2030, according to a study published online Monday.

When global mortality projections were last calculated a decade ago, researchers had assumed the number of AIDS cases would be declining. Instead, it's on the rise.

"It will be increasingly hard to sustain treatment programs unless we can turn off the tap of new HIV infections." - London epidemiology Prof. Richard Hays

Currently ranked fourth behind heart disease, stroke, and respiratory infections, AIDS is set to become No. 3, say researchers in a new report in the Public Library of Science's Medicine journal. It accounts for about 2.8 million deaths every year, but could near 120 million by 2030.

Overall, the researchers predict that in three decades, the causes of global mortality will be strikingly similar worldwide — apart from the prevalence of AIDS in poorer countries. Most people will be dying at older ages of noninfectious diseases like cardiovascular disease, stroke and cancer.

The paper was produced by Dr. Colin Mathers and Dejan Loncar of the World Health Organization. In an optimistic future projection, if new HIV infections are curbed and access to life-prolonging antiretrovirals is increased, 89 million people will die from the disease.

"What happens in the future depends very much on what the international community does now," Mathers said.

These marked differences should spark changes in current approaches to controlling AIDS now, say some experts.

"It will be increasingly hard to sustain treatment programs unless we can turn off the tap of new HIV infections," said Dr. Richard Hays, professor of epidemiology at London's School of Hygiene and Tropical Medicine, who was not linked to the study.

"These AIDS numbers point to a need to do more in prevention."

Public health priorities

Simply focusing on treatment or politically uncontroversial prevention methods will not suffice, officials say.

"You can't put all your eggs in the abstinence basket," said Hays. "We need a menu of strategies for real people," he said, adding that condom distribution as well as new methods, such as a vaccine, are needed.

Mathers and Loncar analyzed data from more than 100 countries. The authors looked at the links between mortality trends and income per capita, as well as other factors, including education levels and tobacco use. Their research also used UN estimates for projected AIDS infection rates and the World Bank's numbers for future income per capita.

Mathers and Loncar then took all of this information and plugged it into a complex modelling equation to predict the top future causes of death and disease.

"This is an important contribution that will help us determine the priorities in public health," said Dr. Majid Ezzati, an associate professor of international health at Harvard University, who was not connected to the paper.

Rising life expectancies

While it may be possible to avert some of the impending damage from HIV-AIDS, Mathers says that other predictions are unlikely to vary significantly.

As populations age, he explains, they are naturally more susceptible to illnesses like cancer and heart disease than from infectious diseases, even in the developing world.

Life expectancy is expected to increase worldwide, with the highest projected life expectancy in 2030 to be in Japanese women, at 88.5 years.

Mathers and Loncar speculate that by 2030, cancer deaths will jump from 7.1 million in 2002 to 11.5 million. The number of deaths from cardiovascular disease is expected to rise from 16.7 million in 2002 to 23.3 million in 2030. Overall, they expect non-communicable diseases to account for 70 per cent of all deaths globally, up from 59 per cent in 2002.

Though economic development may bring better health care, it also has an unfortunate side effect: more road accidents. Based on rates of increasing car ownership, the World Bank estimates that traffic fatalities will increase globally by 66 per cent by 2020.

Some of the road deaths could be avoided if developing countries improve laws and safety practices, Mathers said.