Tests for the bird-flu virus have been conducted at all 133 poultry farms, with results showing no further signs of the bug. The checks were ordered after the 'footprint' of the H5 virus - similar to the one that killed six people in 1997 - was found in chickens at a farm in Ngau Tam Mei in Yuen Long on Thursday. The 15,000 chickens at the farm have been sealed off since then. An Agriculture, Fisheries and Conservation Department spokesman said yesterday that samples collected from the farms were tested and proved to be clear of the H5 virus. About 700 samples had been collected from the infected farm, and Professor Ken Shortridge of the University of Hong Kong's Department of Microbiology said more tests would take about four to five days. Last week, the department found 24 out of 52 blood samples from the farm in Ngau Tam Mei had shown traces of antibodies to H5. Agriculture and Fisheries officers guarded the farm yesterday to ensure no chicken was taken to market. Acting Deputy Director of Health Dr Mak Sin-ping said Hong Kong had a very effective checking mechanism for flu, and the public had nothing to worry about. She said that there had been no cases of H5N1 in the past two years. 'We have a sound flu virus checking system involving public hospitals and private doctors. Members of the public don't have to panic about the recent discovery,' Dr Mak said. She urged the public to be aware of environmental and personal hygiene and stay healthy by eating a balanced diet and doing exercise. 'Of course, the public can continue to consume chickens, as long as they are properly washed and cooked,' she said. People should also wash their hands after contact with animals, especially poultry, she added. The discovery of bird flu in 1997 led to the infection of 18 people and the deaths of six. It led to a worldwide alert, because it was the first time the virus had crossed into humans.