Filed at 9:14 a.m. ET

GENEVA (AP) -- Bird flu is unprecedented in its scope as an animal disease, costing the world's agriculture industry more than $10 billion and affecting the livelihoods of 300 million farmers, the World Health Organization said Monday.

The U.N. agency is meeting in Geneva to discuss global efforts to prepare in case bird flu mutates into a form easily passed between humans, potentially triggering a global pandemic.

Dr. Margaret Chan, who is spearheading WHO's efforts against bird flu, told more than 30 experts that the top priority was to keep the deadly H5N1 strain of bird flu from mutating.

''Should this effort fail, we want to ensure that measures are in place to mitigate the high levels of morbidity, mortality and social and economic disruption that a pandemic can bring to this world,'' she said.

WHO says 174 people are confirmed to have caught bird flu, and 94 of them have died.

Chan said bird flu poses a greater challenge to the world than any previous infectious disease. Since February, the virus has spread to birds in 17 new countries in Africa, Asia, Europe and the Middle East, she said.

''No one can say when this will end,'' Chan said.

Global influenza pandemics -- as opposed to annual recurrences of seasonal flu -- tend to strike periodically. In the 20th century, there were pandemics in 1918, 1957 and 1968.

Dr. Mike Ryan, director of epidemic and pandemic alert and response at WHO, said, ''We truly feel that this present threat and any other threat like it is likely to stretch our global systems to the point of collapse.''

This is the first time world health authorities have tried to stop a global influenza pandemic before it begins. Chan referred to the spread of severe acute respiratory syndrome, or SARS, as evidence of ''how much the world has changed.''

SARS infected 8,000 people, killing 800 of them.

''In a globalized economy, with high volume of international travel, vulnerability to new disease threats is universal,'' she said. ''It is the same for the rich and for the poor.''

WHO spokeswoman Maria Cheng said experts hope to isolate areas where there is a bird flu outbreak and establish agreements allowing international health authorities to respond quickly, testing viruses and implementing containment measures.

Public health measures to quarantine areas, isolate people or help give antiviral medicine to those infected with bird flu also are on the agenda of the meeting, which ends Wednesday.

Even if a pandemic cannot be stopped, WHO says such measures can buy time for health authorities to improve their response strategies and stave off the disease until a pandemic vaccine can be produced.

''Concern has mounted progressively, and events in recent weeks justify that concern,'' Chan said.