"Received through the CRS Web." "Order code RS21288." "Updated January 10, 2003." Title from title screen as viewed on December 1, 2006. Includes bibliographical references.

Smallpox, which kills approximately 30% of its victims, is estimated to have killed between 300 and 500 million people in the twentieth century before the World Health Organizations successful eradication program. The smallpox vaccine is effective at preventing smallpox but has a higher complication rate than any other currently used vaccine. The terrorist attacks of 2001 have increased fears that smallpox might be used as a weapon of terror. Smallpox has several properties that might make it desirable by terrorists, such as contagiousness and high lethality. These factors and its limited availability also make it difficult for a terrorist to use. Most experts agree that it is very unlikely that smallpox will be used as a weapon, but the high consequences of a successful attack have prompted exploration of methods to counter this threat. This report will updated as warranted.