The World Health Organisation, meanwhile, called bird flu a greater global challenge than any previous infectious disease, costing global agriculture more than $10 billion and affecting the livelihoods of 300 million farmers.
Dr Margaret Chan, who is spearheading WHO efforts against bird flu, told disease experts in Geneva that the organisation's top priority was to keep the deadly strain from mutating into a form easily passed between humans. That could trigger a global pandemic.
"This present threat ... is likely to stretch our global systems to the point of collapse," said Dr. Mike Ryan, the WHO's director of epidemic and pandemic alert and response
In Indonesia, a pregnant woman died of suspected bird flu in the capital Jakarta early yesterday, doctors said.
The 25-year-old patient was admitted last week with fever and respiratory problems symptoms of the H5N1 virus that has killed 20 people in Indonesia. She was five months pregnant and the baby also died.
China said the H5N1 virus killed a man in southern Guangdong province, bordering Hong Kong. There had been no reported outbreaks in birds in the area where he died and experts in Hong Kong urged authorities to find the source.
The WHO has confirmed 94 human deaths from bird flu since late 2003, although the virus remains essentially an animal disease that humans contract through close contact with infected birds.
However, the virus is mutating and there are fears it may change enough to be transmitted easily from human to human.
The virus is currently spreading rapidly among wild birds and has reached 15 new countries over the past month, moving across Europe while also hitting Egypt and West Africa.
Austria said the H5N1 virus has been found in several cats in the southern region of Styria a rural area that previously reported outbreaks of the virus in wild swans and ducks.
The three Austrian cats, all of which are still alive, were from the Noah's Ark animal shelter, which took in H5N1-infected birds on February 17.
All the cats have been moved and will remain under observation, while the shelter has been closed.
A dead cat in northern Germany was found to have the virus last week.
The WHO has played down the threat to human health from domestic cat infection, but the news has alarmed pet-loving Europeans. It is thought that cats get the virus by eating infected birds.
Two dead swans found in northern Poland had H5N1, the Polish veterinary institute was quoted as saying on Monday.
The rapid spread of the virus has dealt a heavy blow to Europe's poultry industry, meanwhile, and heightened fears for human health.
Health experts stress there is no risk from eating properly cooked meat, but fears over the virus have dented consumption.
France, which has Europe's largest poultry industry, said it is losing €40 million a month after an outbreak of H5N1 at a poultry farm led more than 40 countries imposing curbs on French poultry products including foie gras.
France announced a new case of H5N1 in a wild duck in the east of the country on Sunday.
A test on a wild swan showed the virus had spread several hundred kilometres south to the Mediterranean Bouches-du-Rhone area.