COPENHAGEN, Denmark (AP) _ Two cases of polio _ the first in Europe since 1998 _ have been diagnosed in Bulgaria, the World Health Organization and Bulgarian officials said Thursday.

Bulgarian health authorities determined in April that a 13-month-old baby, a Gypsy in the Black Sea city of Burgas, had the virus, the WHO said. Other children in the community of Gypsies, also known as Roma, were immediately vaccinated.

However, on May 15, the same virus was identified in a 2-year-old Gypsy child in the city of Yambol, 60 miles west of Burga, health Bulgarian officials reported. The conditions of the ailing children were not disclosed.

Laboratories in Paris, Rome and Atlanta studied the virus and traced it to northern India, according to a statement from WHO's European region headquarters in the Danish capital.

``The fact that the virus was imported from India shows how just how important worldwide vaccination campaigns are,'' WHO spokesman George Oblapenko said. ``Without constant vigilance, Europe's polio-free status and the global eradication efforts would both be in danger.''

The polio virus was last identified in Europe in November 1998, when it was found in a Turkish province along the Iranian border.

Polio has been wiped out in 155 nations, including all of North and South America, China and Australia. But even children in polio-free countries must be vaccinated because infected travelers can easily spread the disease.