Farmers are on heightened alert after an outbreak of bird flu in the North. A three-kilometre zone is in place around a nature reserve in Magherafelt, County Derry, after the virus was found in a small number of captive birds. Chair of the Irish Farmers' Association National Poultry Committee Nigel Sweetnam said the disease has not yet spread to "commercial units". "Avoid contact with wildfowl if at all possible," he said. "Be extra vigilant and report any unusual mortality in birds. "Also, the big message out here is for backyard flock because at the moment it is in the backyard flock, it's not in the commercial units. "But all backyard flocks need to be registered with the Department of Agriculture." The Department of Agriculture here is asking those with poultry or kept birds to take strict precautions.