'The Chinese government has strict regulations on the reporting of epidemics and their disclosure,' said Mr Li Jinxiang, deputy director of the ministry's veterinary bureau.

Blue ear disease - formally known as Porcine Reproductive and Respiratory Syndrome (PRRS) - has infected 290,000 pigs in China this year, Vice-Minister of Agriculture Gao Hongbin said.

That is up from 257,000 that had been infected by late August, according to a toll released by state media.

'We got the disease from abroad and there is no evidence to show it spread from China to anywhere else,' Mr Gao said.

Blue ear disease was first discovered in the United States in the mid-1980s and has since turned up in most pork-producing nations.

'In 1996, China first got the blue ear virus. Analysis this year shows it is 93 per cent the same as the US type,' added Mr Li.

'So China is a victim.'

An outbreak that began in China in May last year killed about one million pigs, causing high fever in adult pigs.

It was later identified as highly pathogenic PRRS, but has not affected humans.

Vietnam reported this month that blue ear disease had again broken out in two provinces, after declaring it eradicated last month.

Epidemiologists are particularly concerned about possible mutations of disease in south China, where humans, pigs and chickens live in close proximity in hot, humid weather.

The spread of the blue ear disease has emerged as a major health concern for China and has been blamed for contributing to a sharp spike in prices of pork, a staple of the Chinese diet.

REUTERS, AGENCE FRANCE-PRESSE