NEW YORK - New infectious diseases have been appearing more often, says a study that suggests "hot spots" where the next new germs are most likely to appear.

"We need to be out there in the hot spot regions looking for the next HIV," said study co-author Peter Daszak.

Daszak, the executive director of the New York-based Consortium for Conservation Medicine at Wildlife Trust, and other researchers present their analysis in Thursday's issue of the journal Nature.

Experts called it the most thoroughly documented report yet to show a past increase in new infectious diseases and to predict where they might appear next.

To designate the hot spots, researchers found 335 appearances of new disease between 1940 and 2004, and then analyzed social and environmental factors that appeared to promote them. Most disease events involved germs new to humans, but researchers also counted illnesses from established germs that had become drug-resistant, moved into a new region or had become much more common.

Decade-by-decade, such incidents grew steadily from 25 in the 1940s to 98 in the 1990s, except for a spike of 103 during the 1980s.

Some proposed future hot spots were for illnesses that emerge from wildlife, as the AIDS virus HIV did from chimpanzees.

The researchers said the highest risk areas are in parts of east Asia, Central America and South America, the Indian subcontinent, Africa, western Europe and some population centres of North America. That's because the historical analysis had found the risk of such diseases goes up with factors like high population density and diversity of wildlife, the researchers said.

Peter Cowen, of North Carolina State University, who didn't participate in the study, called the hot spot analysis "a good guesstimate."