Seoul, Jan 27 : South Korea on Thursday reported the first outbreak of the H5N8 avian influenza virus this winter in a dead wild bird discovered at a river mouth in the southeastern port city of Busan. The highly pathogenic virus was detected in the carcass of a whooper swan found at the mouth of Nakdong River, according to the country's bird flu response headquarters. This was the first H5N8 virus case among 24 highly pathogenic bird flu cases reported since fall. The other 23 were confirmed to be H5N1 cases, Yonhap news agency reported. "Looking back on past cases, the emergence of a new strain can lead to a fast spread of highly pathogenic bird flu," quarantine officials said, calling upon poultry farms to take more thorough measures to prevent virus outbreak. Officials plan to monitor rivers and streams in the southeastern region while prohibiting entrance of farmers and citizens to the mouth of Nakdong River and sterilise farms around the area, including the site where the H5N8 strain was detected. They will also issue an avian influenza alert in places vulnerable to outbreak, such as egg farms. Highly pathogenic avian influenza is very contagious among birds and can cause severe illness and even death, especially among poultry. /IANS