Blue-ear pig disease infected 45,858 swine in 22 Chinese regions in the first five months of the year, Jia Youling, the country's chief veterinarian, said on Monday.

The highly pathogenic disease, also known as Porcine Reproductive and Respiratory Syndrome (PRRS), has killed 18,597 pigs and forced another 5,778 pigs to be culled, said Jia, who is also director of the veterinarian department of the Ministry of Agriculture.

Blue-ear disease was first discovered in the United States in 1987 and spread to China in mid 1990s, he said, adding the virus could not infect humans.

Jia said China first spotted a more virulent form of the pig disease in the summer of 2006 and identified it as a mutated highly pathogenic strain in January of this year.

"The virus has mutated and caused higher mortality rates," he said.

China has twice reported the infections to the Food and Agriculture Organization of the United Nations after pigs in Yunfu, in the southern province of Guangdong, were infected with the virus, said Jia.

Swines dieing from "high-fever diseases" were mainly suffering from blue-ear pig disease but other viruses caused some deaths, said the chief veterinarian.

"Pigs killed by the'high-fever disease' accounted for 0.2 percent of the total pig population," he stated.

Jia maintained that there is no evidence to support the idea that the outbreak of blue-ear pig disease has caused pork prices to jump.

He said the mortality rate of pigs from all causes is now between 6 percent and 8 percent, while in the 1980s, 10 percent of the pig population died before they were slaughtered, said Jia.

According to the Ministry of Agriculture, the price of piglets in April was 71.3 percent higher than a year earlier, while the price of live pigs was 45.2 percent higher, and the cost of pork was up 29.3 percent.

A significant jump in the cost of feed and a decline in the pig population were the major factors behind the rising pork prices this year, the chief veterinarian said.

The pig population declined mainly because pig farmers have incurred losses over the past couple of years and were reluctant to raise them, said Xu Lianzhong, a senior economist with the price supervision center under the National Development and Reform Commission.

"The central government has allocated 280 million yuan (36.5 million U.S. dollars) to fund vaccinations of swine at various pig farms," Jia said.

China successfully developed a vaccine for the new variant in 90 days and approved 12 companies to produce the vaccine in May, he said, adding the government has distributed 20 million milliliters of vaccine to disease-hit regions.

The output of the vaccine would total 70 million milliliters in June, 154 million milliliters in July and 189 million milliliters in August, the chief veterinarian said.

Jia also said the China Animal Disease Prevention and Control Center has set up a reporting mechanism with 2,600 counties nationwide to ensure timely treatment and prevention.