For the first time, according to the Center for Disease Control, unaccounted-for vials of live smallpox virus have been discovered in the United States.

Deadly to humans, smallpox kills about one third of those who contract it. The last known case of smallpox infection occurred in 1978, when mishandling of the virus in a lab spread it to a ventilation system where it infected and killed a man.

Some question why the virus is kept alive if its threat to humans is so great. The answer is research. Many scientists believe that by studying the virus they can gain information as to how viruses work and what allows certain viruses to become epidemic. In the past, research with deadly viruses has led to vaccines and treatments.

Heated debate continues over whether to destroy existing samples of smallpox and other deadly virus strains.

For now, the World Health Organization has once again delayed its decision as to whether or not to destroy the viruses.