African swine fever (ASF), the disease which has hit the world's top pork producer China hard, originated in Africa before spreading to Europe and Asia. It has been found in 50 countries, killing hundreds of million pigs, while reshaping global meat and feed markets.

"We are really facing a threat that is global," OIE Director General Monique Eloit told Reuters in an interview.

"The risk exists for all countries, whether they are geographically close or geographically distant because there is a multitude of potential sources of contamination."

African swine fever, which is not harmful to humans, can be transmitted by a tourist bringing back a ham or sausage sandwich from a contaminated country, throwing it away and the garbage being reused by farmers to feed their pigs, Eloit said.

There are additional risks from trading live animals and food products across borders and from small breeders using restaurant or train station waste to feed their stock.

The disease has spread rapidly to several countries in Southeast Asia including Vietnam, Cambodia, Laos, Korea and the Philippines and more countries are likely to be hit in the coming months.

"In the short term we are not going towards an improvement. We will continue to have more outbreaks in the infected countries. Neighbouring countries are at high risk and for some the question is when they will be infected," Eloit said, stressing that controls were difficult to implement.

The spread of African swine fever has not only ravaged the Asian pig population, but also sent international pork prices rocketing and hit animal feed markets such as corn and soybeans.

It has also weighed on results of agricultural commodity groups due to weaker feed demand for hog breeding.