Oskar Wawschinek, spokesman for the Austrian Health and Food Safety Organisation (AGES), told AFP that mouth swabs taken from the felines on February 22 tested positive to H5N1.
Subsequent testing showed however, that two of the cats no longer carried the virus.
"Nothing remained, nothing developed, they did not become ill" he said, explaining the cats had fought off the virus as humans can fight off a cold virus to avoid becoming sick.
Mr Wawschinek said that the third cat infected with the H5N1 virus was still under observation and was undergoing tests to confirm its presence.
The felines were being kept in the Noah’s Ark animal shelter in Graz, the site of the European Union’s first poultry infection which had been discovered in chickens a week earlier.
On Monday, Noah's Ark's director, Herbert Oster, told AFP that the cats could have come into contact with the birds. The head of the province's veterinary services said transmission probably took place via food or excrement.
AGES is concerned that for a few days at least, the cats were carriers of the highly pathogenic strain of bird flu and could have passed it onto other animals in the shelter.
Further tests were being carried out on the 170 cats that were being kept at the animal shelter, which had now been closed.
Pandemic fears
Health officials across the globe are currently preparing for a feared mutation of the bird flu virus to a form capable of being transmitted between humans.
There has been increased alarm since German authorities announced on March 2 that a cat found dead on the island of Ruegen had H5N1, the first infection of a mammal in Europe.
Initial tests suggest that the animal apparently caught the virus from eating infected wild birds. H5N1 has previously killed domestic and wild cats, including captive tigers, in Asia in 2004 but authorities aren’t taking chances and are investigating all infections, bird or mammal.
The news led hundreds of German cat owners to dump their pets at shelters.
Spreading broadly
- In the latest bird flu developments, the virus was confirmed to have spread to Poland and to Serbia for the first time.
- Hong Kong has imposed restrictions after the neighbouring Chinese province of Guangdong reported a new human victim.
- Hospital officials in Indonesia confirmed a 25-year-old woman who was five months pregnant died with symptoms of bird flu after being in close contact with chickens.
- In Bucharest, five southeast European countries agreed to set up a joint centre dedicated to researching and fighting bird flu.
The H5N1 virus has now killed at least 94 people, according to the World Health Organisation toll, which does not include the latest Chinese victim. It has also lead to the deaths of hundreds of millions of birds.