Scores of deadly infectious diseases are crossing the species barrier from animals to humans, scientists have reported.

A three-year investigation has shown that since 1940 around 250 viruses such as HIV, Ebola Virus, Sars and H5N1 bird flu have jumped from wild animals to people.

Presenting the first-ever map of "hotspots" of new infectious diseases in the British journal Nature, researchers predicted the next pandemic is most likely to come out of poor tropical countries.

It is here where burgeoning human populations most frequently come into contact with wildlife.

The report said that if a monitoring system is not put in place "then human populations will continue to be at risk from pandemic diseases".

HIV/Aids, which has killed or infected as many as 65 million people worldwide, is believed to have jumped from chimpanzees to humans, possibly through hunters who killed and butchered apes.

Most new diseases come from wild animals, especially mammals, which are the most closely related species to humans.

Pathogens that adapt to humans can be extremely lethal, as we have no resistance to them.

"We are crowding wildlife into ever-smaller areas, and human population is increasing," said the report's co-author Marc Levy.

"Where those two things meet, that is a recipe for something crossing over."

Areas that present the biggest potential source for new diseases are East Asia, the Indian sub-continent, the Niger delta and the Great Lakes region in Africa.

More than 20 percent of emerging infectious diseases derive from a growing imperviousness to drugs in certain bacteria, such as extremely drug-resistant tuberculosis and chloroquine-resistant malaria.