Although recent news headlines about bird flu may be buried on the inside pages of many newspapers and news Web sites, the threat of global pandemic flu remains very real.

Medical experts and scientists from all corners agree that the United States is not at all prepared for such a pandemic. Federal, state and local lawmakers and health care officials are working feverishly to stockpile antiviral medication and mass produce vaccines that could eventually help stop a global outbreak.

Editor's Note: This is the first in a five-part series on bird flu that will be featured throughout the week on FOXNews.com.

"Should it continue along its malignant paths, there's little question it could become one of the most terrible threats to life this world has ever faced ... you stop at one place, it re-emerges at another," Health and Human Services Secretary Michael Leavitt said Monday about the H5N1 virus characteristic of bird flu.

"The avian flu bears the potential for societal disruption of unprecedented proportion," added Homeland Security Secretary Michael Chertoff.

"We're not prepared today," Senate Majority Leader Bill Frist, R-Tenn., a physician, told FOX News recently.

"Right now we don't have a vaccine that can be produced quickly enough. We don't have sufficient treatment in the short term, [we don't have] Tamiflu stockpiled. Our first responders are not prepared today and we don't have the investment in technology to take bug to drug in a short period of time to protect the American people, and that's why we've got to act. We need to act now," Frist said.

Pandemic, avian and seasonal (epidemic) flu are different diseases.

An influenza pandemic is a global outbreak of disease that occurs when three conditions are met:

1) The human population will have little-to-no pre-existing immunity to the new virus.

2) The virus causes serious illness in people.

3) It spreads easily from person to person worldwide.

There is currently no flu pandemic, but the world sees about three per century.

Avian flu, or "bird flu," occurs naturally among birds. The strain of this virus now circulating around Asia and parts of Europe is the H5N1 strain. So far, the H5N1 virus circulating in Asia meets the first two criteria of a pandemic, but not the third.

Seasonal influenza, often just called "the flu," is a contagious respiratory illness caused by influenza viruses that occurs every year. It can cause mild to severe illness and thousands of deaths each year. The best protection against seasonal flu, experts say, is vaccination.

Although it's the bird flu that is making most of the news lately, many in the scientific and medical community say H5N1 may not necessarily be the virus that triggers the next pandemic.

Based on evidence from the three pandemics that hit during the 20th century, pandemic flu strains tend to infect between 25 percent and 35 percent of the population. The worst death rate was seen in the 1918 Spanish flu pandemic, which killed 2.6 percent of those who got sick, or about 40 million people. The 1957 pandemic killed 2 million, and the pandemic in 1968 killed 1 million.

The H5N1 bird flu strain has killed at least 68 people in Asia since late 2003, but so far the virus is not capable of being transmitted from person to person. The fear is that H5N1 will mutate so that it can pass easily among humans.

"It is only a matter of time before an avian flu virus ... acquires the ability to be transmitted from human to human, sparking the outbreak of human pandemic influenza," World Health Organization Director General Lee Jong-wook told a gathering in Geneva last month.

As of Nov. 9, outbreaks of H5N1 were reported among poultry in Russia, Kazakhstan, Turkey and Romania in 2005. Mongolia reported outbreaks of the H5N1 virus in wild migratory birds, and Croatia reported H5N1 among migrating swans in October.

In 2004, a handful of human cases of bird flu were reported in Vietnam and Thailand; additional human cases have been reported in Cambodia, Indonesia, Thailand and Vietnam this year. The World Health Organization reports that 124 human cases have been confirmed since January 2004.

On the other hand, seasonal flu causes an average of 36,000 deaths each year in the United States, mostly among the elderly, and nearly 200,000 hospitalizations, CDC Director Julie Gerberding testified recently before Congress.

"The potential for a human influenza pandemic is a current public health concern with an immense potential impact," Gerberding said.

The CDC estimates that a "medium-level" pandemic — one in which 15 to 35 percent of the U.S. population develops the flu — could cause 89,000 to 207,000 deaths, between 314,000 and 734,000 hospitalizations, 18 million to 42 million outpatient visits and another 20 million to 47 million sick people. The U.S. economic impact could range between $71.3 billion and $166.5 billion, according to Gerberding.

The WHO believes a human flu pandemic could cost the global economy at least $800 billion.

The CDC works with the WHO and governments around the world to increase surveillance of potential pandemics so that dangerous viruses can be identified earlier and more effective vaccines can be produced faster.

Other U.S. agencies, such as the departments of Health and Human Services and Homeland Security, National Institutes of Health and various university centers, are also studying how a flu virus mutates and different methods for growing the viruses used to make potentially life-saving vaccines.

On Nov. 1, the Bush administration released its national strategy to safeguard the American public against the next pandemic flu. The government set up a Web site, www.pandemicflu.gov, as a one-stop shop for all information on pandemic flu and avian influenza.

One of the major obstacles the United States faces in preparing for a pandemic is the mass exodus pharmaceutical companies have made from vaccine production. The companies make little, if any, profit from vaccines — often, they lose money — while on the other hand, they face enormous liability when vaccines cause negative side effects in people who take them.

Many experts welcome offering some financial incentives to drug companies to produce more vaccines and liability-protection legislation for the pharmaceutical industry. They also advocate reducing the regulatory barriers in place that prolong getting new medicines and vaccines to market.

"There's a tremendous burden on pharmaceutical companies … the infrastructure has crumbled," said Dr. Paul Offit, chief of the division of infectious diseases at the Children's Hospital of Philadelphia.

"I think the Bush administration has recognized that, to their credit, that we need to build this infrastructure up again."

Dr. Brian Currie, vice president and senior medical director at the Montefiore Medical Center in Bronx, N.Y., said the current way the government stockpiles vaccines and antivirals at pennies above the production costs and the risk companies take by not being able to sell vaccines that have about a 9-month shelf life make for a grim combination.

Making other products such as Viagra tends to be more of a sure thing — and it's profitable.

However, the power of vaccines cannot be underestimated, these experts say. The government, they say, must do whatever it takes to get companies — public or private — to produce enough to protect the masses.

"Flu vaccine is only good for the year — it goes in the garbage can and it goes on the ledger sheet that you never sold them," Currie said.

"If you wanted to do this logically … there is a real need for public education about vaccines. It's almost like we've lost the insight into how powerful they have been as a preventative medicine tool in the last 50 years. The fixation is on lawsuits on undesirable side effects — real or imagined. People need to get a big picture back."

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Respond to the Writer

FOXNews.com is taking an in-depth look at the initiatives, strategies and policies being employed to prepare the United States and the world against the next pandemic flu.

Stories this week will look at new cell-culture technology that would accelerate the production of flu vaccines; why the United States should not be content to rely upon the stockpiling of one or two antiviral medications or vaccines; how the government and medical community hope to entice pharmaceutical companies back into the vaccine production business through incentives such as financial subsidies and liability protections.

Click back to FOXNews.com tomorrow to read, "Bird Flu Part II: Congress Ponders Liability Protection for Vaccine Makers," in the Politics section.