During the anthrax scare of 2001, when envelopes containing the deadly bacteria were mailed to locations throughout the country, 22 people were infected with the disease. Five eventually died.

The incident, occurring shortly after the Sept. 11 terrorist attacks, underscored the vulnerability of the United States to bioterrorism. Those responsible for the anthrax scare have never been found.

But has our preparedness improved since then? According to many experts, the answer is no.

And anthrax is only one of several bacteria and viruses that could be used in a bioterrorist attack.

"Anthrax is easier to come by and people have used it recently," said Kyle Olson, vice president of CRA, a consulting firm specializing in bioterror under contract to the Department of Homeland Security.

Referring to the anthrax scare of 2001, Olson said, "He/she/they are still out there and may be biding their time and making more. If you can make a little, you can make a lot. That's a scenario that has a lot of people bothered."

Easily Spread and Deadly

The Centers for Disease Control and Prevention classifies six pathogens as Class A bioterrorism agents: smallpox, plague, botulism, tularemia, hemorrhagic fever and anthrax.

Michael Greenberger, director of the University of Maryland Center for Health and Homeland Security in Baltimore, explains that the Class A pathogens share some common traits: they can be easily spread, all of them can be deadly, and even a small dose could cause widespread damage and fear throughout a populated area.

To address these concerns, the CDC in 1999 began to develop the Strategic National Stockpile, a nationwide system of storage facilities with equipment and supplies to address an emergency like a bioterrorist attack.

The SNS would supplement efforts by state and local agencies to respond to a public health emergency. And by most accounts, the stockpile has the equipment to do so.

"The SNS is in pretty good shape," said Olson. "There are multiple stockpiles in numerous sites around the country of drugs, antibiotics, medical equipment, even things like gloves and tongue depressors."

Are Emergency Preparations Inadequate?

How these SNS supplies might reach their intended population, however, is a matter of some concern.

"It's one thing to say that stockpile is in good shape -- it's another thing to say that the preparations for using the stockpile are in good shape," said Olson.

"Very few places in the U.S. have plans for using [the SNS] in place. There are some good efforts, but by and large the majority of American cities do not have good plans or plans that have been tested," said Olson.

Olson and Greenberger note that a handful of cities, like Denver, Seattle and Chicago, have tested some portion of their emergency plans, and say tests are now being planned for other large cities.

But Greenberger said that in large cities like Chicago, "things did not go well."

"The major problem with the stockpile is that once it gets to the field, there are no plans to distribute the medications from the stockpile once they arrive on the scene," he said.

Charles Schable, director of Terrorism Preparedness and Emergency Response for the CDC, believes great improvement in coordinating the distribution of emergency supplies and medication has been made in recent years.

"We know that states and U.S. territories are much more prepared than in recent years and could adequately respond to an event, but there is more work that needs to be accomplished," Schable said in an e-mail to ABCNEWS.com.

"Each state has a plan and the plans are very thorough right down to crowd control. And many states have initiated training exercises involving the federal stockpile to the disbursement of antidotes by setting up public clinics," he said.

"In each training exercise, gaps were uncovered and the lessons learned are modifying each state plan," Schable added. "But as I have already said, our preparedness effort is improving but more work needs to occur."

'Underfunded and Understaffed'

Coordinating the distribution of emergency medical supplies involves a number of local government agencies, some of which are already facing funding and staffing problems.

"Distribution networks within the states and cities have not been worked out. It has proven to be a problem in field tests," said Greenberger.

"Police and fire departments are very understaffed across the country," Greenberger went on, adding that many first responders who also serve in the military reserve have now been called into military duty overseas.

"Many fire chiefs and police chiefs say their departments are in worse shape now than they were on Sept. 10, 2001," Greenberger said.

Adding to that problem is the burden that public health agencies must bear. "State and city health departments are underfunded and understaffed," Greenberger said.

"All the responsibility falls on their shoulders -- it's a classic unfunded mandate situation."

Greenberger is also concerned about the real-world implications of public health emergency plans outside of middle-class suburbs and towns. "When you get to the inner city, very little attention has been paid to it," he said.

"I'm very concerned about the problem of inner city residents who don't have doctors and who don't have cars," Greenberger said. "Citizen preparation is more talk than action."

Is Bioterrorism Masking the Real Problem?

As serious as bioterrorism concerns may be, others feel that the real problem is hiding in plain sight: our lack of public health preparedness for naturally occurring strains of bacteria and viruses that may pose a greater and more immediate threat.

The current shortage of flu vaccine is just the most recent example of how limited our resources are for dealing with known problems.

"Sometimes you tend to disregard the obvious," said Dr. Kathleen F. Gensheimer, state epidemiologist with the Maine Department of Health and Human Services. "We really are missing what's staring us right in the face."

"I'm not downplaying five deaths from anthrax," Gensheimer said, "but we have 38,000 people dying of influenza each year."

Even in cases where vaccines and antibiotics are available, the supply of these medications is unreliable. "There have been shortages of several antibiotics," said Gensheimer. "It's a symptom of the whole system. We really are vulnerable."

"And people still don't have any clue what we're talking about when we say 'influenza pandemic,' " said Olson. The Spanish Flu of 1918-19 killed at least 25 million people worldwide in just those two years -- more than died in World War I.

Experts fear the U.S. drug supply is woefully unprepared for a pandemic of this magnitude.

"The U.S. does not have a robust infrastructure for developing antibiotics -- they're viewed as low-priced commodities," said Olson, "increasing reliance on off-shore manufacturers. The fact is we don't have the ability to ramp up to produce these drugs."

This article is third of a three-part series.