Influenza (search) — the flu — can keep victims in bed for a week with a runny nose, achy head and sore throat, but what are the chances the pesky virus will be used as a weapon of mass destruction?

A group of scientists from the University of Texas (search) says it could indeed be weaponized if dangerous strains get into the hands of terrorists.

The Texas researchers wrote in the Journal of the Royal Society of Medicine that scientists are close to completing the blueprint of the 1918 Spanish Flu (search) that killed 20-40 million people around the world, including half a million in the United States. That blueprint, they said, could provide the recipe for terrorists looking for a deadly weapon.

The researchers cite other flu pandemics within the past 100 years that have wreaked havoc around the world, including the "Asian Flu" of 1957-58, which caused about 70,000 deaths in the United States, and the "Hong Kong Flu" of 1968-69, which caused about 34,000 U.S. deaths.

"In addition to such spontaneous mutations, we must, since the terrorist attacks of September and October 2001, consider the possibility of malicious genetic engineering to create more virulent strains," the scientists warned.

But other experts disagree.

"Anything is possible," said pathologist Miles Jones, the medical director of Net Doctor International (search). "Is it highly likely? At this point, no."

Although it's usually transmitted through direct contact with someone infected with the flu, influenza can also be spread by aerosol. The effectiveness of this method of transmission, combined with the fact that the virus is readily accessible, boosts the chance it could be by a terrorist, the researchers said.

The scientists say terrorists could spray aerosol containing the weaponized virus inside a plane to set off an epidemic. The flu could be attractive to terrorists because of the virus' short incubation period and the fact that post-exposure immunizations don't help cure it, they said.

"Even a natural epidemic of influenza can devastate our health-care system and render society vulnerable to terrorist attacks of any kind," the scientists wrote.

Influenza viruses cause epidemics almost every winter. According to the Centers for Disease Control and Prevention (search), these winter flu epidemics can cause illness in 10-20 percent of people living in the United States and are associated with an average of 36,000 deaths and 114,000 hospitalizations per year.

"Just about any microorganism can be used as a BT [bioterrorism] agent and CDC tries to prepare for all of them," said a CDC spokeswoman. But "we have not singled the flu out as being any potential, specific threat."

Other experts agree that influenza hasn't yet shown up on the radar screen as a potential weapon of mass destruction.

"I'm not so worried about it," said Peter Brookes, senior fellow for national security affairs at The Heritage Foundation (search). "I think if it were a serious candidate for a weapon of mass destruction, somebody would have it in their stockpile. And as far as I know, nobody does."

That "somebody" usually means Russia, China, North Korea or Syria — countries known to have possessed, at one time or another, various chemical, biological and nuclear weapons such as anthrax or ricin.

But whether a substance could be used as a weapon of mass destruction really depends on how easily the enemy can get its hands on it, how much it costs and how easily it can kill.

"I think it's going to come down to what's available," Brookes noted.

Rich Pilch, a scientist in residence at the Monterey Institute of International Studies' Center for Nonproliferation Studies (search), said it is possible that someone could alter the gene areas of the flu to cause a very harmful strain, but "that's really more of a natural threat."

"I would certainly worry about it as far as a natural threat," Pilch said. But he adds that it's an unlikely terrorist threat: "It just doesn't seem like a very easy weapon to get hold of and produce — I think that's a very unlikely possibility."

Another strike against the flu as a potential weapon is that, like viruses such as West Nile, it's likely that the elderly or very young would be the people most likely to die from it. Most normal, healthy adults would probably be able to ward it off, experts said.

But the Texas scientists note that it's because of this that the flu poses a greater threat to world leaders in particular than something like smallpox. Most world leaders, they wrote, are older and prone to influenza and its cardiovascular implications.

This runs counter to the very deadly effects of other substances, such as ricin. Ricin can cause paralysis and a fairly quick and painful death. Sarin is another quick and effective weapon: It's a colorless and odorless gas, lethal in doses as small as .5 milligrams and can kill less than 10 minutes after exposure.

Although the scientists said public health officials may not consider outbreaks of the flu a sign of a terrorist attack, Jones noted that the CDC and the World Health Organization's (search) response to the recent SARS (search) epidemic has been "remarkable and exemplary" and that they could effectively handle a flu epidemic.

The current risk?

"People don't need to go around wearing masks at this point in time," Jones said.