Several European countries have reported outbreaks of a severe strain of bird flu in wild birds, and France has raised safety checks to counter the virus, which can have a major impact on farmers.
Though the highly pathogenic H5N8 virus is very contagious in birds, it has never been found in humans. It was found in several European Union countries in 2014 and led to massive poultry cullings.
The World Health Organisation for Animal Health (OIE) said Germany, Austria, Croatia and Switzerland have officially reported outbreaks, which concern a particularly virulent strain affecting wild birds. France's Agriculture Ministry said that H5N8 has also been found in Hungary, Poland, the Netherlands and Denmark.
Austria and Switzerland on Thursday took precautionary steps to prevent the spread of the virus to domestic poultry after discovering cases of the disease in wild ducks around Lake Constance, which borders the countries along the Alps.
The Dutch government took similar steps earlier this week, when it ordered farmers in the Netherlands to keep poultry flocks indoors following the outbreak.
France, the European Union's largest agricultural producer, had imposed stricter controls and banned duck and goose production in 17 administrative departments to contain the 2014 outbreak of the bird flu virus.