In his first inaugural address in 1933, President Franklin Delano Roosevelt inspired a battered nation with these words: "The only thing we have to fear is fear itself -- nameless, unreasoning, unjustified terror which paralyzes needed efforts to convert retreat into advance."
Instilling fear is a terrorist's stock in trade. But as FDR knew, the best antidotes to unreasoning, unjustified terror are knowledge, strength, and preparedness. Seventy years after he spoke those words to a nation beaten down by the Great Depression, we again face an uncertain economic future, and the even grimmer prospect of biological terrorism.
Many people pick at their skin once in a while, but sometimes it crosses the line into a condition called skin picking disorder (excoriation).
When this happens, picking at the skin -- for example, picking a scab or the skin around your nails -- can become so frequent and intense that it causes bleeding, sores, and scars.
Some people with this disorder repeatedly scratch to try to remove what they see as some kind of imperfection in their skin.
Biological terrorism, or bioterrorism, is the use of disease-causing agents to spread death and destruction and strike fear into the heart of a target population.
It has an ancient and dishonorable history: In the Dark Ages, armies used catapults to fling plague-ridden corpses over castle walls. In 1763, British commander Lord Geoffrey Amherst ordered the distribution to Native Americans of blankets that had been used by victims of smallpox. And in more recent times, biological weapons were used against livestock and civilians during both World Wars.
"In theory, biological weapons could be even more devastating than chemical or nuclear weapons. That's because some of them can spread far beyond the initial point of release through ongoing and multiplying human-to-human transmission," write David Ropeik and George Gray, PhD, from the Harvard Center for Risk Analysis in their book Risk: A Practical Guide for Deciding What's Really Safe and What's Really Dangerous in the World Around You.
The U.S. Centers for Disease Control and Prevention (CDC) divides biological agents into three categories -- A, B, and C -- based on their ability to wreak havoc on the population at large. Category A or "high priority" agents are those that can be easily transmitted through human contact, have a high death rate and the potential for a major public health impact, may cause widespread panic and disruption, and require special public health measures. Agents in this category are in alphabetical order: