The ongoing FBI investigation into two cases of anthrax in Florida is illustrating both the possibility and the limitations of a major biological attack occurring in the United States.
Both cases involve employees for the supermarket tabloid The Sun. The first man died last Friday, while the second has been treated for the disease and is in stable condition.
While authorities have not officially labeled the incident as terrorism, the fact that two men from the same office building contracted anthrax seems to indicate some form of foul play, say experts. Health officials say the disease is not contagious, and so could not have been passed from one man to the other. This may mean that a criminal or terrorist group has the ability to grow or manufacture anthrax spores, and might attempt to carry out other attacks in the future.
But the chances of any group successfully pulling off a wide-scale anthrax attack are still fairly remote, medical experts say. While certain terrorist groups may now be able to grow the anthrax organism, they would face many technical obstacles in preparing and deploying the spores to infect large numbers of people.
In addition, the relatively quick reaction of Florida health officials in identifying and isolating the outbreak indicates another strong layer of defense that could mitigate the impact of any future attack.
"What is the likelihood of a major chemical or biological attack in the United States? Very slim," says Christopher Hellman, a senior analyst at the Center for Defense Information in Washington. Even given what's just happened, he says, "you're way more likely to be hit by lightning."
Experts say one of the main reasons anthrax is often seen as conducive to a terrorist attack - aside from its deadliness - is that the spores are relatively hardy.
"You can keep them in your pocket for 20 years, and they're still viable," says Theresa Koehler, an associate professor at the University of Texas Medical School at Houston.
But to spread the spores effectively, terrorists must first find a way to get large numbers of people to inhale them - something that makes them dependant on things like weather conditions, if they're planning their attack outside. Once the spores settle on the ground, they're far less dangerous, since it's unlikely they'd be inhaled.
Terrorists would also have to have the technical expertise to manufacture the proper particle size - since anthrax has a tendency to clump, which makes it less effective.
"Anthrax spores can survive for days, but it's not so easy to disperse them in the air in the proper-size particles," says Jacqueline Cattani, director of the Center for Biological Defense at the University of South Florida.
The closest thing to a historical precedent officials have for judging the potential impact of an anthrax attack is a 1979 explosion at a military research facility in the Russian city of Sverdlovsk. The explosion released anthrax spores into the atmosphere - but only a relatively small percentage of residents came down with the disease, Dr. Koehler says.
And while terrorist groups have attempted to use anthrax in the past, most have been unsuccessful. "The Japanese cult Aum Shinri Kyo tried to disperse anthrax about nine times in Japan before the sarin gas attacks - and were totally unsuccessful," says Ms. Cattani. "In this particular case, it's unfortunate one person did die, but I think the public health department dealt with it very rapidly."
Jennifer LeClaire in Miami contributed to this article.