Boston ? Americans are so ill-informed about smallpox that a majority believe the deadly disease still breaks out naturally throughout the world and can be cured, a Harvard survey found.

The last case of smallpox was 25 years ago. And while halting the natural spread of the disease was one of the greatest public health victories in history, there is no cure. Not yet.

Misconceptions like these suggest a deep public misunderstanding of smallpox, despite months of discussion about the possibility of a bioterrorist release of the virus.

“It’s staggering,” said Robert J. Blendon, who directed the survey at the Harvard School of Public Health.

Among the survey’s findings:

• 30 percent believe there has been a smallpox case in the United States in the past five years, and 63 percent think there has been one somewhere in the world. Actually, the last U.S. case was in 1949 and the last in the world was in 1977.
• 25 percent said it was likely they would die from the vaccine. The actual death rate from the shots is estimated to be less than three per million.
• 78 percent said they thought medical treatment for smallpox would prevent death or serious illness. Actually, there is no proven treatment after symptoms start.
• 16 percent think the country has enough vaccine to give everyone in case of a smallpox attack. The government says it has enough for all.
  ¢ 58 percent do not believe that vaccination within a few days of exposure will prevent people from contracting smallpox. Actually, it will.