International trade will halt as countries close their borders. There will be major shortages in products that mean life and death, such as food and drugs. And when the pandemic is over, the question will be how to get the world's economy going again.

In a collection of articles published Thursday in the journal Nature, scientists sketch out a scenario in which a strain of bird flu, which usually would not be dangerous to people, adapts to become highly contagious and deadly to humans.

The scientists warn that not enough antiviral medicines are stockpiled and that there are no human vaccines yet. There also are no plans in most countries to cope with the health and economic disaster the scientists say would result.

Also Thursday, in Washington, D.C., the Health Subcommittee of the U.S. House Energy and Commerce Committee will hear testimony from leaders of industry and federal health agencies on steps being taken to prepare for a pandemic.

Vaccines Are Not Available

In Nature, Albert Osterhaus and colleagues at Erasmus Medical Center in Rotterdam, the Netherlands, cite a World Health Organization estimate suggesting that within months of the start of a pandemic, nearly 30 million people would be hospitalized and as many as 7.5 million would die.

They call on WHO to assemble a task force made up of experts in such fields as human and animal health, agriculture and ecology.

The World Health Assembly, WHO's governing body, ended a 10-day meeting in Geneva on Wednesday calling on member states to develop pandemic plans and urging WHO director-general Lee Jong-wook to "seek a solution to the current global shortage of influenza vaccines," a statement said.

Potential to Trigger Next Pandemic

Bird flu, which has killed millions of birds and has been found in 10 countries, most recently in wild geese in China, has killed 53 people. It "has the potential to trigger the next pandemic, which, judging from history, is well overdue," writes Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, in Nature.

Clinical trials of vaccines have begun. But without more factories and new technologies to make it possible to produce millions of doses quickly, Fauci writes, "we may experience again the devastation of past pandemics," such as those in 1918, 1957 and 1968.

Though some countries, such as the United States, have begun planning, "preparation worldwide is insufficient," Osterhaus said in a telephone interview. "Vaccines are not available, and stockpiles of antivirals are insufficient at the moment."

Could Take Down Global Economy

There is still uncertainty about when a pandemic might emerge, says Michael Osterholm of the University of Minnesota's Center for Infectious Disease Research and Policy. But "the accumulation of evidence is very disturbing."

In his Nature article, Osterholm calls WHO's pandemic plan "non-specific" and says it "falls far short of what is needed" for local or long-term planning.

Development of a vaccine should be a top priority, he says, along with availability of antivirals and protective masks.

The danger goes beyond public health, he warns.

"Even if a country had access to a protective pandemic vaccine its economy is going to crash," he says. International trade will halt as countries close their borders. "We will see major shortages in products that mean life and death," such as food and drugs, he says, and when the pandemic is over, the question will be how to get the world's economy going again.

"How do you prime a pump when you have no electricity?" he asks. "Nobody has ever seen the global economy go down."