Smallpox
Smallpox is a potentially deadly infection caused by the variola virus. The infection causes severe illness, including a high fever, followed by a rash all over the body that looks like blisters.
Smallpox symptoms develop about 12 days after exposure. The disease usually is not contagious until the rash first appears. As scabs form, the chance of passing on the disease decreases.
Smallpox was a worldwide problem in the past. But because of a widespread vaccination program, it was declared eradicated (no longer a naturally occurring disease) by the World Health Organization (WHO) in 1980.
There may be a risk that the smallpox virus could be stolen by people in order to threaten or harm others.
Chickenpox and Smallpox Rash Comparison
Source: The U.S. Centers for Disease Control and Prevention (CDC).
| Chickenpox | Smallpox |
|---|---|---|
| How initial symptoms differ | 0 to 2 days of mild illness pass before the rash develops. | 2 to 3 days of severe illness pass before the rash develops. |
| Lesions first appear on the face or trunk. | Lesions first appear in the throat or mouth, then on the face, or on the upper arms. | |
| How the rash lesions differ | Lesions develop in successive fashion. While some are new, others are crusting over (in "crops"). | Lesions develop at the same time, and they look alike on any one section of the body, such as the abdomen, arms, or face. |
| Lesions change rapidly, crusting over within 24 hours. | Lesions change slowly, scabbing over after 9 to 15 days. | |
| Lesions sit on the skin surface and look like small blisters. | Lesions become firm, dome-shaped, and deep in the skin. | |
| Rash rarely develops on palms and soles. | Rash commonly develops on palms of the hands and soles of the feet. | |
| Lesions are most concentrated on the torso, with fewest on the hands and feet. Lesions can affect the face and scalp, but rarely affect the entire body equally. | Lesions are most concentrated on the face, hands, and feet. |
How is smallpox treated?
There is no known cure for smallpox. Treatment includes drinking plenty of fluids and taking medicines to control pain and fever. To prevent the spread of the virus, an infected person must be kept away from other people until he or she is no longer contagious.
How can you prevent smallpox?
People who have survived smallpox cannot get it again.
Also, there is a smallpox vaccination. It has vaccinia virus in it, which is like the smallpox virus but safer. If you get the shot before you've been exposed to smallpox, it will likely protect you for at least 3 to 5 years. And having a second shot later can protect you for an even longer period of time.
The shot works even if you don't get it in advance. Most people who get the smallpox shot within 3 days after they've been exposed to the virus will have no symptoms or will have symptoms that aren't as severe. Getting a shot 4 to 7 days after exposure may also help.
People who have very close contact with a person who has gotten a smallpox vaccine can get an infection from the virus used in the vaccine. The infection usually causes a minor skin rash and is not smallpox. So the site where the smallpox vaccine was given should be covered until the scab falls off.
In the past, when a smallpox infection was diagnosed, infected people were kept away from others to prevent the spread of infection. Everyone who might have been exposed to the virus was then vaccinated. This practice, called ring vaccination, played a key role in wiping out smallpox. Many experts think it would be better to carry out ring vaccination before mass vaccination if there were a case today.
Because there are risks of a serious reaction from the vaccine, routine smallpox immunization doesn't occur. All children and most adults in the U.S. today have a chance of getting infected if they are exposed to the smallpox virus.
Since the September 2001 terrorist attacks on the U.S., more vaccine has been made. The U.S. government has enough smallpox vaccine for all Americans in case of an outbreak.
The smallpox vaccine is recommended for laboratory workers who handle the vaccinia virus, for members of smallpox response teams, and for certain people in the military. For accurate, up-to-date information, visit the Centers for Disease Control and Prevention (CDC) website at www.bt.cdc.gov/agent/smallpox.
How is smallpox diagnosed?
If a doctor suspected a case of smallpox, blood and skin tests would be needed to confirm the diagnosis. A confirmed case of smallpox would be considered a worldwide health emergency. In the U.S., state and federal health officials would quickly take action. They would keep anyone who might have been exposed away from others.
If a smallpox outbreak had been confirmed, a doctor in the outbreak area could diagnose smallpox without a lab test. The doctor would look at the rash and ask about symptoms and possible exposure to the disease.
How does smallpox spread?
Smallpox is contagious. It can be passed from one person to another through coughing, sneezing, or breathing, or by contact with the scabs or the fluid from blisters. It can even spread from an infected person's personal items and bedding. Smallpox is easiest to spread during the first week of the rash. As scabs form, the person is less contagious. But a person can spread the virus from the time the rash first appears until all scabs have fallen off.
If a terrorist were to release a small amount of the virus into the air, it is possible that it could spread among a large number of people. The virus may be able to survive and infect people for up to a day.
People who get this disease must stay away from others to help prevent it from spreading. If there has been a smallpox outbreak and you think you might have been exposed, call your doctor or local health department. Do not go directly to a health facility, because you could pass the disease to other people.
What is smallpox?
Smallpox is a contagious infection caused by the variola virus. Smallpox can be deadly, so if an outbreak happens, it is vital to stay away from infected people. Get vaccinated if you have been around someone who has smallpox. And if you have symptoms, seek medical care.
The telltale signs of smallpox are severe illness with a high fever, then a body rash. Symptoms appear about 12 days after the person is infected.
Before there was a vaccine, smallpox used to cause death all around the world. Thanks to widespread use of the vaccine, the last natural case of smallpox occurred in 1977. And in 1980 the World Health Organization (WHO) declared that the spread of smallpox was stopped and that the disease had been wiped out.
Because there is a slight risk of serious reactions and even death from the smallpox vaccine, routine smallpox immunization ended in the United States in 1972.
Smallpox virus is known to exist in labs at the Centers for Disease Control and Prevention (CDC) in the U.S. and at the State Research Center of Virology and Biotechnology in Russia. But it may also be in other labs. Some people worry that terrorists could release the virus and spread smallpox to many people.
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