1.   Among the reasons that Lederberg changed his mind, he said, was that he had been overly optimistic about what could be learned from mapping the smallpox virus.

2.   Assuming terrorists have the smallpox virus, or could buy or steal it, could it pose a threat?

3.   Because the smallpox virus exists only in laboratories, experts say the threat that terrorists may lay their hands on it is remote.

4.   -- After a momentary reprieve, the smallpox virus seems headed for destruction, after all.

5.   A dispute continues on whether to preserve the smallpox virus itself for future study.

6.   A magnified image of Variola major, the smallpox virus.

7.   After a reprieve, the smallpox virus seems headed for destruction after all.

8.   After several stays of execution, the smallpox virus, one of the biggest killers in history, is back on death row.

9.   But deliberately released smallpox virus, plague bacteria or some other pathogen might spread widely before it is ever detected, they said.

10.   But you can only truly test a replacement for it against real smallpox virus.