The highly pathogenic blue-ear disease hit 22 provinces during the first five months of this year, killing 18,597 pigs, the country's chief veterinarian said yesterday.

Also known as Porcine Reproductive and Respiratory Syndrome (PRRS), the disease was found in 45,858 pigs, leading to the culling of 5,778, said Jia Youling, director of the veterinary bureau affiliated to the Ministry of Agriculture.

Within three months of the disease being identified, a vaccine was developed; and the ministry has authorized 12 factories to produce the vaccine, Jia said.

The Ministry of Finance has allocated 285 million yuan ($37.13 million) toward free vaccines for smaller breeding farms, where the disease was widespread last year.

Jia told a news briefing that the blue-ear disease, identified in January, broke out last May with provinces along the Yangtze River region hardest hit. About a million pigs died of what was then known as "high-fever disease" last year.

"The disease caused panic, but the pig death rate last year was actually within the normal range of 6 to 8 percent. The 'high-fever disease' accounted for only 0.2 percent of the fatalities."

Jia said the disease is not transmitted, or harmful, to humans but "it spreads very quickly among pigs".

He also said the outbreak had partially led to recent hikes in pork prices "but the main reason was the big price increases of animal feed that began last June".

Pork prices rose 35.5 percent in April and 10.4 percent in May to about 17.4 yuan ($2.27) per kg, according to official figures.

The ministry has ordered pig breeders to establish a nationwide immunization system; and implemented a complete ban on the sale, transport and processing of pigs that die from diseases.

More than half of the world's pigs are raised in China and residents consumed 50 million tons of pork last year.