BEIJING -- China's Ministry of Agriculture on Tuesday warned the country's pig breeders that they are entering the peak season for the highly pathogenic blue-ear disease, also known as Porcine Reproductive and Respiratory Syndrome (PRRS), which has already killed 18,000 pigs this year.

Between January and May, 45,000 pigs contracted the disease, but a ministry source failed to specify what provinces and regions had reported outbreaks. Earlier reports said south China's Guangdong Province and Guangxi Zhuang Autonomous Region had reported outbreaks.

The source said 12 factories are producing new-type vaccines for the disease, under the supervision of China's Veterinary Medicine Supervisory Institution.

The ministry has instructed PRRS-affected regions to implement all disease control measures and prevent the infection from spreading.

Pig breeders have been ordered to establish a nationwide immunization system, which covers disinfection and proper treatment of dead animals and of their excrement.

The ministry has also implemented a complete ban on the sale, transport and processing of pigs that have died from the disease.

It is also establishing a central monitoring system for signs of PRRS virus mutations, which should be completed by the end of June.

The ministry has dispatched inspection teams to supervise disease control and prevention work.

The outbreaks have contributed to rising pork prices in some areas. It is believed the price hikes will help raise the country's consumer price index, or CPI, to a new high for May.