As a case of avian flu was confirmed in a cat in Germany, veterinary experts meeting in Paris said no country should consider itself safe from it and it was "highly likely" the flu will continue its spread in poultry stocks in Europe and beyond.
"The risk now is high for everybody," said Bernard Vallat, director of the Paris-based World Organisation for Animal Health, which is hosting a two-day meeting of experts from 50 countries.
However, the World Health Organisation (WHO) and disease experts said the discovery of a cat with the disease probably did not increase the risk to humans from a virus which has killed at least 93 people since late 2003.
The cat was found at the weekend on the Baltic Sea island of Rügen, where Germany's first bird flu cases were identified in dead swans two weeks ago.
Officials at the Federal Research Institute for Animal Health said tests were still to determine whether the cat died of the strain that spread to humans with fatal consequences in Turkey and Asia.
"It has been known for some time from Asia that cats can infect themselves with the virus by eating infected birds," said Thomas Mettenleiter, president of the institute.
"I wouldn't let any cat wander around in any area where birds in any mentionable number have perished from a H5N1 infection," said Dr Hans-Dieter Klenk, a biologist specialising in infections to Spiegel.
Albert Osterhaus, a virologist at the Erasmus Medical Centre in The Netherlands who has conducted research into the virus in cats, said he was not surprised by the case.
"Cat-to-human transmission is theoretically possible and not to be excluded. We have seen cat-to-cat transmission in laboratory experiments.
"People should keep their cats inside in regions where the disease was found," Mr Osterhaus said.
Elsewhere, the flu continued its relentless spread with Sweden becoming the ninth EU country to confirm the arrival of the virus even though it is not yet known if it is the N1 strain of the H5 flu virus.
In Africa, Niger became the second sub-Saharan African country after Nigeria to confirm the potentially deadly strain of the disease and suspected poultry outbreaks in Ethiopia, Gabon, Gambia and Sierra Leone were also under investigation, the WHO said.
Health experts have gone to the southern Bahamas island of Inagua to find out if an unexplained spate of bird deaths was linked to an outbreak of the flu.
Over the past two days, 15 of the island's famed flamingos, five roseate spoonbills and one cormorant have been found dead with no external injuries on the island just to the north of Haiti.
In Ireland, there were 50 reports of dead birds to the Department of Agriculture's special phone line up until late last evening.
The department said anyone who found and handled a bird which may have bird flu would be given advice on what to do by the public health authorities.