SEOUL, Jan. 3 (Xinhua) -- Over 30 million chickens and ducks have been culled in South Korea in less than 50 days as a highly pathogenic strain of avian influenza (AI) spread rapidly nationwide, Yonhap news agency reported.

As of Tuesday, the number of poultry destroyed for the bird flu infection reached 30.33 million since the first case was discovered at a farm in Haenam county, South Jeolla province, the country's southwest region, on Nov. 16.

The figure accounted for almost 20 percent of 165.25 million poultry raised in the entire country.

The speed of spreading, however, slightly slowed in the past week, during which 3.84 million chickens, ducks and quails were infected, or 12.8 percent of the total contagion.

Cautiousness remained over the prolonged contagion given that the AI spread lasted in South Korea for 195 days in 2014, slaughtering 13.96 million poultry.

The agriculture ministry has raised the AI crisis level to the highest in its four-tier system.

Egg prices have surged recently as 32.1 percent of total layer chickens, which lay eggs, or 22.45 million chickens, were culled for the H5N6 virus infection.

Given that chicks take over six months to become hen to lay eggs, egg prices are expected to remain high for the time being.