South Korea will disinfect farms around the country over the new year and limit the transport of animals, stepping up its effort to contain an outbreak of foot-and-mouth disease that has spread close to the capital as well as bird flu.

The foot-and-mouth among hogs had been limited to the center of the country until this week but a case has now been confirmed at a farm just 50 km (30 miles) from Seoul in the north of the country.

The outbreak began five months ago, raising fears about food safety. Nearly 23,000 hogs have been destroyed to contain the outbreak, according to a statement from the agriculture ministry on Tuesday.

All the cases have involved a type of the disease that animals are inoculated against in South Korea. The ministry said additional vaccine would be given to farms in affected areas and all farms in the country would be disinfected on Dec. 31 and Jan. 1.

The late July outbreak was the first in more than three years but it came as authorities struggled to contain a problem with bird flu, which has pushed up the price of pork as consumers bought alternative meat.

In its statement, the ministry said more than 40 poultry farms, mostly in southeastern provinces, plus a market near the capital had been affected since late September and 526,000 birds had been slaughtered. No humans have been infected.

The livestock disease problems are a big factor behind a jump in pork imports, mainly from the United States and Germany. These rose 21 percent to 328,241 tonnes in the first 11 months of the year from the same period in 2013, South Korean customs data showed.