11.   Cowpox virus is harmless but the smallpox virus, though closely related, is one of the most devastating viruses known.

12.   Destruction of the smallpox virus, known as variola, would be the last step in the smallpox eradication program and the first deliberate extinction of a species.

13.   Fields also led a fight to preserve the smallpox virus, which was originally scheduled to be destroyed this year but was given a reprieve.

14.   Ewald contends a threat continues to exist, because large stockpiles of smallpox virus remain in Russia.

15.   For ages, the smallpox virus struck humans, taking millions of lives.

16.   He said that the smallpox virus would be a poor biological-warfare agent but that it could be very effective in creating panic.

17.   He said that the material included anthrax bacteria and the smallpox virus and that North Korea had the means to mass-produce biological and chemical weapons.

18.   It begins with a natural virus called vaccinia, a close relative of the smallpox virus.

19.   It involves isolating cases and vaccinating those with whom such individuals have come in contact after being exposed to the smallpox virus.

20.   It is based on vaccinia, a close but harmless relative of smallpox virus.