The head of the World Health Organization warned Thursday that infectious diseases will spread more easily in the future due to globalisation, changing lifestyles and rising population densities.

"The future looks very bright for microbes, not so good for humanity," Margaret Chan told a luncheon in her hometown Hong Kong, the site of a major outbreak of the SARS virus in 2003 that killed almost 300 people in the city.

Higher population density, industrialisation of food production and the increase in international travel have provided many opportunities for communicable diseases to spread, she said.

"Given this unstable and unpredictable situation, only one generalisation is possible -- there will definitely be more new diseases capable of causing outbreaks in humans," Chan said at the event organised by the Asia Society.

But the WHO head said not all new diseases will be as "devastating" as the outbreak of SARS that killed more than 800 people worldwide and the H1N1 epidemic that caused at least 17,000 deaths.

Chan said one reason that infectious diseases have been on the rise in the region and China was due to the habit of eating the meat of exotic animals, as most new diseases are spread from animals to humans.

"Constant mutation and adaptation are survival mechanisms of the microbial world, these organisms are well equipped to take advantage of every opportunity to jump the species barrier," she said.

The WHO issued a global alert in September for a SARS-like coronavirus which killed two people in Qatar, one in Saudi Arabia and two in Jordan.

The WHO says the coronavirus detected in the Middle East this year was unrelated to SARS and is a novel form of the germ.