WASHINGTON – The United Nations’ stark warning that avian flu could arrive in America within six months or less has brought to light the country’s unpreparedness for a pandemic expected to infect 75 million people and debilitate 40% of the country’s work force, medical analysts said yesterday.

“This will be 50 times worse than Katrina,” the co-director of the Pandemic Preparedness Initiative at the Trust for America’s Health, Kimberly Elliott, said of America’s ability to respond to the crisis.”Katrina was a regional tragedy. This will be everywhere, at the same time.”

The U.N.’s avian influenza coordinator, David Nabarro, warned on Wednesday that the disease, which has spread among birds from Asia to Europe, could result in a North American outbreak in six to 12 months, possibly sooner. According to Dr. Nabarro, flight patterns of migratory birds could bring infected fowl to Alaska from Africa, then south, resulting in a mainland outbreak of the H5N1 strain of avian flu.

The warning prompted immediate concern on Capitol Hill yesterday, as a spokeswoman for Senator Stevens, Courtney Boone, told The New York Sun that the announcement “provides a greater sense of the time line of what Senator Stevens is concerned about.” In January, Alaska’s senior senator expressed frustration that the Centers for Disease Control maintains no laboratory for avian flu testing in Alaska. While the U.S. Geological Survey screens fowl in the state, Mr. Stevens said the samples are sent to laboratories in Michigan, then to the CDC in Atlanta, delaying results by months.

While Dr. Nabarro’s warning applies to an outbreak among birds, not humans, Alaska lawmakers have cautioned that Inuit and other native communities in rural parts eat migratory birds, increasing the likelihood of spreading the disease to humans.

Senator Murkowski, also a Republican of Alaska, said the state is “working with our Native communities and our hunters, who are likely the first to be in contact with migratory birds in rural Alaska, to ensure they have the necessary information on what steps and procedures to take.”

Meanwhile, in comments to radio host Hugh Hewitt, Senate Majority Leader Bill Frist warned yesterday that state and federal authorities are “woefully underprepared” to enforce quarantine provisions and distribute medicine, food, and other vital supplies in response to an avian flu pandemic. Dr. Frist pledged to spend “a good deal of my time evaluating our ‘lessons learned’ from Katrina and how to improve our preparedness in the event of a pandemic.”

According to doctors and scientists, however, the federal government is years away from adequately addressing a flu crisis.

Health professionals yesterday said that the most pressing problem was a lack of vaccines. The federal government has said it needs 600 million doses of bird flu vaccine, two per person, to inoculate every American.

Scientists yesterday said America has around 2 million doses stockpiled. The president of the Infectious Diseases Society of America and the chairman of the Department of Medicine at New York University, Martin Blaser, said even those supplies were outdated, based on an old strain that did not respond to the flu’s ongoing mutations.

“Right now it would take us probably close to 36 months to produce enough vaccine to cover everyone, using the existing manufacturers,” Ms. Elliott said. Currently only one facility in America, the Swiftwater, Pa., plant of French-owned Sanofi Pasteur produces H5N1 vaccines in significant quantities. Under a $7.1 billion plan announced by the Bush administration in November, it will take until 2010 before America can produce enough vaccine for every American in a six-month period.

Moreover, Dr. Blaser said, America is using a 50-year-old technology to develop vaccines, by incubating the flu in chicken eggs. A France-based ISDA fellow, Dr. David Fedson, told the Sun yesterday that the National Institutes of Health had failed to address avian flu as a public health issue, squandering limited vaccine resources to create the optimal immunization for an individual, instead of an adequate vaccine for a population of 300 million.

Also inadequate, analysts said, was government planning for the peripheral effects of the disease. The devastating 1918 influenza outbreak affected around 5% of the worldwide population, Ms. Elliott said, and the World Health Organization has warned countries to anticipate a 25% infection rate – around 75 million Americans.

“What the government is telling businesses, and nonprofits, and civil society is that you should think about having 40% of your workforce out over a period of months,” Ms. Elliott said. In addition to the infected, those missing work include laborers taking off to care for sick relatives; parents taking off to care for children in the event of school closures, and “the worried well”: otherwise healthy people who avoid the workplace for fear of exposure.

Ms. Elliott said the Bush administra tion was working on a government-wide response that includes, for example, closing down airports if there are too few air-traffic controllers; intervention by the Treasury Department to avoid the collapse of financial markets, and the maintenance of law and order.

Comparing the disaster to Katrina, scientists observed that the hurricane was a one-time event that could be cleaned up with aid from the rest of the country. Since flu outbreaks come in waves – the 1918-19 epidemic had three – churches, charity groups, and state and local governments would face a sustained assault without external assistance, since every locality would be dealing with their own crises simultaneously.

New York, the analysts said, is one of the best-prepared areas in the country owing both to the work of the state – which released its revised bird-flu plan late last month – and of the city, led by the deputy commissioner of the Department of Health overseeing bird-flu preparations, Dr. Isaac Weisfuse.

Despite America’s lack of preparedness, scientists urged calm in response to the U.N. announcement, cautioning that an outbreak among the avian population was unlikely to infect humans.

The sentiment was echoed by representatives of the poultry industry. A spokesman for the National Chicken Council, Richard Lobb, said yesterday that the vast majority of American poultry are raised indoors – kept away from the migrating ducks and geese that carry avian flu. Free-range chickens, which he said represent only around 1% of America’s poultry production, would be moved inside in the event of an outbreak.

Mr. Lobb added that around 94% of poultry companies are participating in a voluntary bird-flu testing program. Large chicken processing companies like Tyson and Purdue, Mr. Lobb said, will destroy any broiler flock that tests positive. Surrounding flocks will also be tested and destroyed.

In countries where the flu had shifted from birds to humans, families maintained their own chicken flocks and, upon finding a sick bird, killed the flock and exposed themselves directly to the bodily fluids and organs of diseased poultry, Mr. Lobb said, adding that such transmission was unlikely to occur here.