The discovery by the German authorities on the island of Rügen was swiftly followed by a decision by the Swedish Board of Agriculture to introduce emergency measures from Wednesday morning.
“All Swedish poultry which is not already indoors must be taken inside,” said Leif Denneberg, the chief veterinarian at the Board of Agriculture.
“If that is impossible then they must be fed and watered protected under a roof. There will also be restrictions on the display of poultry.”
Denneberg said that the virus had reached the vicinity of Sweden earlier than expected and did not rule out the possibility that swans from Sweden were on Rügen even now.
Experts had expected the H5N1 virus to arrive in the Baltic between mid-March and mid-May.
“It’s remarkable that the disease is already here,” said Leif Denneberg.
“It could be that the cold in the Balkans has made the birds migrate earlier. But it could also mean that the virus is more widespread than we thought.”
The restrictions in Sweden apply not only to commercial poultry but also to all private owners of hens and other fowl.
The H5N1 strain, which has killed about 90 people in Asia, Turkey and northern Iraq, has also been detected in wild birds and poultry in Romania, Bulgaria, Ukraine, Croatia, Italy and Greece.
No human cases have been reported so far in Europe.
Sweden also ordered poultry inside late last year after the deadly disease first arrived in Europe, but at that time the restrictions only applied to the Stockholm region in the east of the country and the Gothenburg region in the southwest.