Sweden has become the latest European country to report a case of bird flu. A duck found dead west of Stockholm had a mild type of the H5 avian influenza virus but not the deadly form that has killed more than 60 people in Asia. So far the aggressive strain has been found in several countries to the east of Europe including Turkey, Romania and Russia. Each has introduced strict measures such as culling all wild fowl and poultry to try and contain the outbreak.Samples from dead swans in Croatia have confirmed the presence of H5 and authorities say they will now be slaughtering some ten thousand poultry. Emergency procedures are also being taken in Russia’s Chelyabinsk region near Kazakhstan where avian flu was discovered two days ago. The village of Sanuli has been quarantined and all infected birds have been destroyed. Even pigeons were killed as part of the measures. The H5N1 strain can be caught by people if they have prolonged and close contact with infected birds. Some experts fear it could mutate to transfer between humans and lead to a global outbreak of flu.