Facts About Smallpox Disease

U.S. plan developed for possible outbreak

Early Smallpox Pustules On The Face Of An Infant
Smith Collection/Gado / Getty Images

The Disease

According to the Centers for Disease Control and Prevention (CDC), smallpox is an acute, contagious, and sometimes fatal disease caused by the variola virus. Symptoms of smallpox begin with high fever, head and body aches, and sometimes vomiting. A rash follows that spreads and progresses to raised bumps and pus-filled blisters that crust, scab, and fall off after about three weeks, leaving a pitted scar.

A person exposed to smallpox virus will initially have no symptoms and is not contagious. Sometime between 7 and 17 days later, symptoms will begin. The person becomes most contagious once the rash begins, and remains contagious until the last smallpox scab falls off.

The Threat of Smallpox

Smallpox, if used as a weapon, would be a serious threat because:

  • it is spread through the air when an infected person breathes, talks, laughs, or coughs
  • it can also be spread by infected clothing or bed linens
  • it can spread in any climate or season
  • there is no treatment or cure
  • few doctors would know smallpox if they saw it
  • people who survive it are left with ugly scars on their bodies or face, and some become blind
  • 30% or more of people who contract smallpox die

Smallpox devastated the American population in the 1700s (see Elizabeth Fenn's book, Pox Americana, for the details). Anyone who knows about it fears it.

Once a few cases were reported in the media there would be widespread concern, even panic.

What is Being Done About a Possible Outbreak?

Since the last case of smallpox occurred in 1977 in Somalia, scientists have had to rely on research that was done before then, plus their best educated guesses, when trying to plan for an outbreak.

Here's what we know, and what is being done:

1. People vaccinated many years ago may not be immune.

Vaccination gives immunity to a disease, but not forever; scientists generally agree that full immunity only lasts 3-5 years. After that, it begins to fade. A study published in 1972 showed a death rate of 11% for people vaccinated more than 20 years prior to exposure to smallpox.

Scientists do know that if someone is exposed to smallpox, giving the person the vaccine within 4 days reduces the severity of the disease or even prevents him/her from getting it.

2. National Smallpox Preparedness Program

In December 2002 a U.S. National Smallpox Preparedness Program was initiated to protect Americans against smallpox, should it be used as a biological weapon. Smallpox Response Teams are to be formed in communities throughout the country. Teams members, including health care workers, firefighters, police, and volunteers, are vaccinated against smallpox and thus could respond to an outbreak without contracting the disease. The Department of Defense also began vaccinating military and civilian personnel deployed to high-risk areas.

During January 24-December 31, 2003, smallpox vaccine was administered to 39,213 civilian health-care and public health workers throughout the U.S. More than 1 million military and support personnel have also received the smallpox vaccination since December 2002.

3. CDC Smallpox Response Plan and Guidelines

The CDC has developed a Smallpox Response Plan and Guidelines. The plan outlines strategies which would guide the public health response to a smallpox outbreak at the federal, state, and local levels. The CDC states that smallpox vaccine is not available for members of the general public at present. However, in the event of an outbreak, the agency states there is enough smallpox vaccine stockpiled to vaccinate every person in the United States.

4. Educating health care providers about vaccination

An added consideration is that training doctors and nurses how to administer smallpox vaccine properly and recognize a successful reaction to the vaccine (a sore at the injection site) will be an ongoing process.

Smallpox is not given in a single shot (injection) like other vaccinations. There is a special technique used called multiple puncture vaccination. Health care providers must also teach those who are vaccinated about symptoms that may occur, and how to take care of the sore at the vaccination site.

Want to Know More?

The CDC has Smallpox Basics and a Vaccine Overview available for the general public. There is also an information page on What We Learn About Smallpox From Movies--Fact or Fiction which discusses the FX Networks 2005 TV movie "Smallpox" and the May 2002 ER finale.


 Altman, Lawrence K. "Effect of Smallpox Vaccine May Be Longer, Study Says." The New York Times, 8/29/02.

Centers for Disease Control. Smallpox.