PARIS, April 7 (Reuters) - The bird flu outbreak that has recently killed 50 people in Asia and cost the region billions of dollars could spread to other parts of the world, the global animal health body OIE said on Thursday.

"The potential for the disease to spread to other continents is real and the international scientific community cannot remain insensitive to the challenge of preventing this happening," OIE Director-General Bernard Vallat told a conference in Paris.

The H5N1 influenza virus, which has killed people in Vietnam, Thailand and Cambodia since it hit Asia in 2003, has also devastated trade and led to the destruction of tens of millions of chickens and other birds across the region.

A strain of the disease has recently surfaced in North Korea, causing a cull of hundreds of thousands of chickens.

Experts fear that if the H5N1 virus mutated into a more contagious form, it might unleash a global flu pandemic that could kill millions of people.

Vallat said the best way to control the disease was to tackle it at source, with a combination of culling and vaccines.

"Disease control needs to be more effective by creating early detection and rapid response systems. Veterinary services need access to better diagnostic tools and efficient, cost-effective vaccines," the Paris-based OIE, a body that sets global animal health standards, said in a statement.

Francois-Xavier Meslin of the World Health Organisation (WHO) said 79 human cases of bird flu had now been reported in three countries with a "frightening" 62 percent fatality rate.

He said indications of possible changes in its clinical effects on humans and an increase in the number of reported clusters of human cases were worrying signs and the WHO was "on alert" for the possibility of a pandemic emerging.

Bird flu was first seen to jump from birds to people in 1997 in Hong Kong, when it infected 18 people and killed six.

DAMAGE SEEN UP TO $12 BILLION

The virus has devastated the poultry trade in many Asian countries, and investment bank CLSA said this week the crisis had already cost the region $8-12 billion.

The European Union has extended its ban on poultry meat and live bird imports from eight Asian nations until September.

"Increasingly, corporate analysts rank avian influenza as one of the major risks, along with a banking crisis, civil unrest and armed conflict, which could derail the Asian region´s current economic expansion," said Samuel Jutzi, Director of the Animal Production and Health Division of the FAO.

The disease has become so entrenched because the virus thrives on small farms where chickens often mix with wild ducks, believed to be carriers of the disease, experts say.

"The current situation in Asia has strong links with traditional animal production and marketing systems, including backyard and subsistence poultry production, multiple animal species farming with chickens, ducks and pigs," Vallat said.

"Recent research has also confirmed that aquatic birds, especially ducks, can act as reservoirs of infection with or without clinical signs and are capable of excreting viruses into the environment," he added.

"Countries should review their poultry marketing systems to obtain a higher level of biosecurity," the OIE (Office International des Epizooties) said.

Vallat said the two-day conference would officially launch a new OIE/FAO network of scientists, known as OFFLU, to help in disease diagnosis and management. The OIE would also link up with the WHO to provide virus isolates from animals which could be used to produce human vaccines soon.