Avian Flu Detected in the Netherlands and Britain LONDON - Health officials moved to combat outbreaks of bird flu at poultry farms in Britain and the Netherlands on Monday, culling thousands of chickens and ducks to avert the spread of infection. On Sunday, the Dutch authorities blocked the transportation of eggs and poultry across the country after a strain of the flu was detected at a farm in Hekendorp, south of Amsterdam. The strain was said to be lethal for poultry and potentially transmissible to humans. The authorities ordered the slaughter of 150,000 chickens at the farm. News reports identified the strain as H5N8, which has never been detected in humans, according to the European Center for Disease Prevention and Control in Stockholm. The strain has been reported in birds in South Korea, China, Japan and, earlier this month, in Germany. "This highly pathogenic variant of avian influenza is very dangerous for bird life," the Dutch government said. The disease can be transmitted from animals to humans. In Britain, the Department for Environment, Food and Rural Affairs said that a case of the virus had been found in ducks at a farm in the Driffield area of East Yorkshire in the north of England, but that the risk to public health was "very low." While the exact strain was still being investigated, the outbreak was not caused by the lethal H5N1 strain and "there is no risk to the food chain," the department said. The authorities are apparently eager to ensure that, just weeks before Christmas, news of the outbreak does not harm the poultry business at one of its busiest periods. Health officials ordered the culling of all 6,000 ducks on the British farm and imposed a six-mile restriction zone around it, the department said. It was not clear if the cases in Britain, the Netherlands and Germany were linked, but officials said one line of investigation was to determine whether a wild bird had transmitted the disease to the farm in Yorkshire. "We'll be looking for other possible sources of the disease, including any links to the disease that we're seeing in the Netherlands and Germany," Britain's chief veterinary officer, Nigel Gibbens, told the BBC, "and that will include looking at the risk from wild birds spread to our national flock." "The link to the disease that they found in Germany and the Netherlands is our most likely source," he said. The outbreaks of bird flu in recent days prompted the European Union on Monday to move toward issuing a warning across the Continent, aimed mostly at reassuring importers outside the bloc that the bulk of poultry from the European Union is unaffected, according to Enrico Brivio, a spokesman for the European Commission, the union's executive arm. The Dutch authorities have gone beyond European requirements, dating to 2005, by ordering a nationwide ban of movements of poultry meat, live poultry eggs and other poultry products, Mr. Brivio told a daily briefing. The case in Yorkshire was less of a concern than the case in the Netherlands, he added. "In Holland we have a very high density of poultry," said Mr. Brivio. But in Yorkshire, "there is not such a high density" and so "we think, for the moment, the decisions taken by the British authorities are adequate." European health experts were expected to meet on Thursday to review the situation.