As thousands of scientists around the world destroy a deadly flu (search) strain accidentally sent to thousands of labs for testing, lawmakers on Capitol Hill questioned just how such a potentially disastrous move could have been made and what it means for America's security.

In a letter sent to Homeland Security Secretary Michael Chertoff (search), Rep. Edward Markey (search) on Wednesday asked how such a dangerous strain of the flu could have been put in motion and what could be done to prevent the virus from falling into the hands of potential terrorists and how to stop any further security breaches.

Click here to read Markey's letter (pdf file) .

"How did a deadly virus get mailed like a postcard to 3,700 laboratories?" the Massachusetts Democrat asked. "If the H2N2 virus is released and infects even one person, it has the potential to spread like wildfire and wreak havoc across the world. I am extremely concerned about the consequences of sending this virus to thousands of unsuspecting and unprepared laboratories that may not be equipped to recognize or handle such a dangerous virus."

Markey, a member of the House Homeland Security Committee, also planned on asking Chertoff in person how such an incident can be avoided in the future.

The World Health Organization (search) began urging the world's labs to destroy H2N2 (search), an almost 50-year-old pandemic flu virus, after it was discovered that the germ was sent in kits by Meridian Bioscience, Inc. (search) as part of proficiency testing to nearly 5,000 labs — mostly in the United States. The kits were part of a routine quality-control certification test conducted by the College of American Pathologists (search).

A Canadian lab alerted the WHO that the sample was from the 1957 flu pandemic, which killed between 1 million and 4 million people and which is supposed to be kept in high-security biological labs. It has not been included in flu vaccines since 1968; anyone born after that date has little or no immunity to it.

Dr. Julie Gerberding, head of the U.S. Centers for Disease Control and Prevention, said Wednesday there is no sign that people around the world are being infected.

"There's a lot of questions right now we don't have answers to," CDC spokesman Tom Skinner said, referring to the agency's failure to learn how such a dangerous strain was included as part of the testing process. "I think what people need to understand is the very labs that receive these strains of influenza all have people trained to work safely and effectively with these viruses."

While some industry experts, such as those with the American Council of Health (search), have called for a review of the professionals involved in the transactions, the near-frantic situation was stark notice in an era in which a biological or other attack would severely strain America's public health system, especially if the attack were to cause an epidemic.

"The incident is a chilling reminder of the nation's vulnerability to a major flu epidemic — a crisis for which America is dangerously unprepared," Sen. Edward Kennedy, D-Mass., said Wednesday.

"Hopefully it is a loud wake-up call for action by Congress and the administration to expedite the urgently needed investments in hospitals and all our other public health defenses, before this alarming series of errors becomes a massive national tragedy. Whether it happens accidentally or because a terrorist causes it, the devastation will be the same."

The flu scare came on the heels of $16 million anti-terrorism drills dubbed "TOPOFF" (search), carried out in New Jersey and Connecticut last week. In the drills, public health officials, emergency responders and law enforcement tried to find weak spots in America's emergency planning systems and push the nation's emergency medical response system to the breaking point.

"It's our firefighters, our police officers, our emergency medical personnel who rush to the scene" in the case of an attack or emergency, Sen. Susan Collins, R-Maine, said of the drill. "And the burden is first on local first responders, county, state officials to respond, and that's why this exercise which brings together all levels of government is so important."

Senate Majority Leader Bill Frist said the flu fiasco further underscores the need to bolster America's domestic and global public health infrastructure.

"As strains grow resistant and immunities expire or viruses reassert, becoming more lethal and transmissible, we are at greater risk for a potential pandemic outbreak, as these viruses are only a plane ride away," said Frist, R-Tenn., who is a heart and lung transplant surgeon.

"Last year's shortage of the flu vaccine exposed America's vulnerability to a potential outbreak of emerging infectious diseases," he said. "And the extensive and necessary precautionary measures taken to prevent the spread of the H2N2 virus highlight the need to move forward with legislative solutions."

Frist spotlighted the need to strengthen the U.S. domestic vaccine supply, expand legal protections, encourage collaboration between the public and private sectors and advance research and development.

Markey said the flu incident also raises questions about the number and types of people with access to biological materials that could potentially trigger a global pandemic. He added that a strong system needs to be instituted to limit access to such dangerous materials and reduce the potential for an accidental or intentional release of such pathogens.

"The public deserves to know whether this case was a serious breach of security or if the current oversight system allows companies to recklessly ship deadly pathogens across the country and overseas without any safeguards to protect the public," he said.

Among other questions, Markey wants Chertoff to answer whether U.S. facilities that work on dangerous pathogens are secure enough so they can't be used by terrorists to manufacture bioweapons, as well as whether individuals working at such facilities are able to ship pathogens anywhere in the world. In addition, Markey wants to know whether Homeland Security has a mechanism in place to require someone shipping pathogens that could be converted into biological weapons to notify the agency.