Asian countries might be hard-pressed to adopt Hong Kong's bio-security measures at wet markets to fight an ongoing bird flu crisis, a Food and Environmental Hygiene Department official said. Assistant director Rhonda Lo Yuet-yee said the retail markets in countries where bird flu was endemic were different from those in Hong Kong. 'Our wet markets are in enclosed buildings. Their wet markets are just a roof, open on both sides. They also have some wet markets which move every day,' Ms Lo said. She said the portable wet markets were different from the usual Sunday markets in Europe, where dry goods were sold. All sorts of animals are traded in Asian markets. 'The wet markets move about because residents usually buy a week's supply of food.' The simplest measure that endemic countries could implement was to segregate animal species at farms and retail markets, she said. Ms Lo also said bio-security measures and vaccination would remain important components of Hong Kong's anti-bird flu plan. 'Hong Kong is a high-risk area. It is surrounded by countries with the bird flu problem. It is always being challenged by countries on all sides, so we still need to continue with vaccinations,' she said. Hong Kong has experienced four bird flu outbreaks since 1997, when the H5N1 strain first jumped the species barrier, killing six out of 18 people infected. It has been bird flu-free since 2003, despite an ongoing outbreak that has affected 11 countries, including the mainland.