Smallpox Health Facts

Published November 1, 2002
  • Smallpox spreads from person to person, primarily via droplets or aerosols expelled from the throat of infected persons, by direct contact, and via contaminated clothing and bed linens. It is fatal in perhaps a third of previously unvaccinated victims.
  • Smallpox virus no longer occurs in nature, but is limited to two legitimate repositories, one in the United States, the other in Russia (and perhaps illegitimately in a very small number of other countries). It is, therefore, very difficult to obtain, and also to cultivate and disseminate.
  • Smallpox is not immediately contagious. It becomes contagious only after an incubation period and appearance of the characteristic rash, by which time the victim is prostrate, bedridden, and probably hospitalized. Therefore, the scenario in which a terrorist infects himself and spreads the disease widely through the population is not a realistic one.
  • Although smallpox vaccination in the United States ended in 1972, individuals who were vaccinated prior to that time retain significant immunity as a result of these immunizations, both against contracting smallpox and against a fatal outcome in case of infection.
  • Public health authorities have at their disposal various proven epidemiologic and medical interventions. Early detection, quarantine of infected individuals, surveillance of contacts, and focused, aggressive vaccination—an approach dubbed “quarantine-ring vaccination”—are the essential elements of a control regime.
  • The government has taken steps to cope with the possibility of a terrorist attack involving smallpox by educating doctors to recognize the disease and by vaccinating small teams of experts who can rush to any part of the country to contain and treat a suspected outbreak.

Source: Henry I. Miller and Sherri Ferris, “Bioterrorism, Anxiety, and the New Normalcy,” American Council on Science and Health, November 15, 2001.