A quarantine officer (R) checks the temperature of a passenger arriving from Britain at the Incheon international airport, west of Seoul, April 30, 2009. Countries should be on high alert for the new swine flu virus, tracking any suspect cases and ensuring medical workers do not spread it further, the World Health Organisation said on Thursday. REUTERS/Choi Jung-In/Yonhap (SOUTH KOREA HEALTH TRAVEL SOCIETY) NO SALES. NO ARCHIVES. SOUTH KOREA OUT. NO COMMERCIAL OR EDITORIAL SALES IN SOUTH KOREA