The African swine fever spreading rapidly in China is "here to stay", the United Nations (UN) Food and Agriculture Organization (FAO) said on Friday, adding that it was almost certain to spread to other Asian countries.

The fever was first detected in China in early August and has been found in 18 farms or abattoirs in six provinces, with many cases more than a 1 000 kms (621 miles) apart, the FAO said in a statement.

With pork such a popular meat in many Asian countries, the FAO said the spread of the virus to China's neighbours is a near certainty, and likely through movements of products containing infected pork.

"The geographical spread, of which ASF has been repeated in such a short period of time, means that transboundary emergence of the virus, likely through movements of products containing infected pork, will almost certainly occur," said Juan Lubroth, chief veterinary officer at FAO.

The response to the disease is "extremely challenging" because the virus can survive for months in meat products, animal feed and swill, said the FAO.

China has banned the transport of live hogs in provinces where infections have been reported, a move that has idled traders, crowded farm pens with unsold pigs, and left slaughterhouses short of stock.

Pork prices in the country's populous south have spiked as demand rises ahead of a week-long holiday in October and highlights the prospect of imports.

Lubroth said the most likely explanation for the vast distances the virus has spread in China is through processed or raw pork products and less likely through the movement of live animals.

Experts at an emergency meeting hosted by FAO in Bangkok this week agreed to set up a regional network to collaborate and respond when new outbreaks occur anywhere in the region.