Americans first grappled with the reality of bioterrorism during the 2001 anthrax attacks. Those attacks, which left five dead and 17 seriously ill, have yet to be linked to a suspect, but they did provide a wake-up call for government officials who are now trying to determine how to best prevent possible future bioterror attacks.

What is bioterrorism?

Bioterrorism is the intentional use of organisms such as viruses and bacteria to harm or kill people.

In many cases the targets of these attacks are civilians, not the military. People or countries may use this method of attack because it is a way of harming their opponents without directly engaging in military combat or other types of overt warfare.

Bioterrorism has been used throughout the centuries. In the 6th Century B.C., the Assyrians poisoned the wells of their enemies with a deadly fungus. In 1346, during the an attack on the Black Sea town of Kaffa, the Tartar army hurled plague-ridden bodies over the walls of the city. In 1767, during the French and Indian War, the English gave blankets laced with smallpox to Native Americans loyal to the French.

According to experts, the biggest bioterror hazards now are anthrax and smallpox, although other possible threats include bubonic plague, botulism and tuberculosis.

The smallpox threat

Officials are concerned that smallpox could be used as a biological weapon by terrorists who wish to harm the United States. The smallpox virus, which was eradicated worldwide in 1980, is a highly contagious disease that can kill up to 30 percent of individuals infected. Routine smallpox vaccination was stopped in the U.S. in 1972, and the vaccine is only available through the Center for Disease Control (CDC).

The virus is currently stored in two World Health Organization repositories, one in Russia and one in Atlanta, GA. However, some believe that countries like Iraq have secret supplies as well.

According to the CDC, a smallpox outbreak could spread rapidly, since few people have an immunity to the virus and many health personnel might fail to recognize its symptoms. Plus, Americans' increased mobility could allow smallpox to more easily spread.

To vaccinate or not?

There is no proven treatment for smallpox. However, the vaccine can be given up to four days after initial exposure and still be effective. But there are risks. According to statistical figures from the 1960s, for every million people vaccinated, one person will die from complications, 12 will contract postvacinial encephalitis and 39 will contract eczema vaccinatum.

Children less than one year old, pregnant women, individuals with a weakened immune system and people with skin conditions should avoid vaccination unless directly exposed to the virus, the CDC says.

President Bush's plan

On Dec. 13, President Bush ordered vaccinations for members of the military serving in high-risk areas of the world. His order applies to hundreds of thousands of military personnel and defense workers. He also said that he will take the vaccine, but that members of his staff and family will not.

The president will make vaccinations available for more than 450,000 medical workers -- those most likely to encounter a person with smallpox, including state response team members and emergency workers.

Public health agencies will work to accommodate citizens who insist on being vaccinated, although they will not be encouraged to get it, according to President Bush.

Differing opinions

While health officials agree that a reaction plan is necessary, some think the vaccine's risks are too great and that vaccination should wait until a real threat occurs.

The method of vaccination is also being debated. Some endorse a "ring vaccination" method in which only infected people and those who came in contact with them would be vaccinated until an outbreak is contained. But some, who worry the virus could spread faster than health workers could contain it, endorse vaccinating all Americans against smallpox.

What do you think? Should all Americans be vaccinated against the threat of smallpox? Or should only limited numbers of people receive the smallpox vaccination? Click here to share your opinion.

-- By Annie Schleicher, NewsHour Extra