Smallpox

Smallpox is one of the most potent bio-terror weapons available. It is a highly contagious disease that is unique to humans and caused by the Variola virus. Smallpox transmission generally occurs through face-to-face contact, direct contact with contaminated fluids and objects, and through the air. About 30 percent of those who become infected with smallpox die from the illness.  However, it is anticipated that transmission rates and mortality would be much higher if the virus was used in a deliberate attack today, as the immunity in the population is extremely low and dropping day by day. Few illnesses have had as profound an effect on human health as smallpox. In the 20th century alone, an estimated 300 million people died of smallpox.

There is no treatment for the disease

It would be very simple to use the virus as a weapon