Italian health officials have announced a range of emergency measures after the country's first discovery of the deadly H5N1 strain of the bird flu virus.
Infected wild swans have been found in southern Italy
The health minister is holding a crisis meeting with regional officials.
The virus was confirmed on Saturday in wild swans in the south, the same day a UK laboratory found cases of the virus in swans from Greece and Bulgaria.
On Sunday, Slovenia said it had discovered the H5 strain in a swan and had sent a sample to the UK for tests.
Italy will create a 3km (2 mile) protection zone around each outbreak site and a surveillance zone of 7 km.
It will also test samples of domestic birds inside the protection zone and separate poultry from contact with domestic birds.
Greece adopted similar measures on Thursday after dead swans were found near Thessaloniki, Greece's second-largest city. A UK laboratory confirmed the H5N1 virus in the swans.
The same laboratory also found the deadly bird flu virus in wild swans from the Bulgarian wetland region of Vidin, close to the Romanian border.
The UN's Food and Agriculture Organisation warned this week that bird flu could already have arrived in countries neighbouring Turkey, where outbreaks have hit 26 of its 81 provinces.
The H5 case in Slovenia was found less than 10 km (6 miles) from the Austrian border, according to the European Commission.
Samples have already been sent to the UK laboratory for further tests to determine whether it is a variety of the deadly H5N1 strain.
Slovenian health officials say they are taking the same precautionary measures as the authorities in Italy, Greece and Bulgaria.
A 3 km (2 mile) protection zone around the area where the swan was found has been established and a surveillance zone of 10 km has been put in place.
Slovenia has also been in touch with Austrian officials as the surveillance zone crosses the Slovenian-Austrian border.
Meanwhile, a World Health Organisation-sanctioned laboratory has confirmed two more human bird flu deaths in Indonesia.
Tests carried out on two women who died last week showed that they had the H5N1 strain of the virus.
The women, both in their 20s, were from the east Jakarta suburb of Bekasi.
This brings the number of Indonesian victims to 18.
On Friday, China confirmed a 20-year-old Hunan woman as its eighth victim.
And in Nigeria, health officials are investigating whether outbreaks in poultry in northern Nigeria have spread to humans.
Two children in the northern state of Kaduna were said to be ill. The H5N1 virus was detected there on Wednesday.
The H5N1 strain of bird flu has killed at least 90 people since early 2003, mostly in South-East Asia.