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What should I know about smallpox?

Smallpox is caused by the variola virus that emerged in humans thousands of years ago. Smallpox infects only humans, and the last natural case of smallpox in the world occurred in 1977. 

Is the smallpox virus still around?

Except for laboratory samples at the Centers for Disease Control and Prevention (CDC), the smallpox virus has been eliminated. However, there is concern that the smallpox virus could be used as an agent of bioterrorism. For this reason, government and public health officials are taking precautions for dealing with a smallpox outbreak and have developed detailed nationwide smallpox response plans.  

What are the signs and symptoms of smallpox?

The symptoms of smallpox begin with high fever (101 -104oF), head and body aches, and sometimes vomiting. These symptoms generally appear 7 to 19 days (with an average of 10 – 14 days) following exposure. A rash, most prominent on the face, arms and legs, follows in two to three days and will usually spread to all parts of the body within 24 hours. As the rash appears, the fever usually falls and the person may start to feel better. The rash starts with flat red bumps that develop at the same time. The raised bumps become pus-filled blisters that crust early in the second week. Scabs develop and fall off after about three weeks, leaving pitted scars.

How do people get smallpox?

Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from one person to another. A person with smallpox is sometimes contagious with onset of fever, but the person becomes most contagious when the rash appears. Once the rash appears the person is usually very sick and not able to move around in the community. The infected person is contagious until the last smallpox scab falls off. 

Contaminated clothing or bed linen can also spread the virus. Special precautions need to be taken to ensure that all bedding, clothing, and other surfaces patients have come into contact with are cleaned with disinfectants like bleach and quaternary ammonia. 

Smallpox is not known to spread by insects or animals. It is rare for smallpox to be spread by virus carried in the air in enclosed settings, such as buildings, busses, and trains.  

What is the difference between smallpox and chickenpox?

Smallpox is sometimes confused with chickenpox, but several features of these diseases are significantly different:

  • The initial symptoms of smallpox are much more severe than those of chickenpox. Smallpox has severe symptoms like muscle aches and high fever. Chickenpox has mild symptoms that may not be noticeable before the rash appears.
  • Smallpox rash is most common on exposed portions of the body: face, forearms, wrists, palms, lower legs, feet, and soles. Chickenpox is most common on covered areas of the body.
  • Smallpox bumps tend to be at the same stage of development, and they happen all at once. With chickenpox, it is common to have more than one occurrence of bumps and they may keep coming back. Smallpox bumps tend to be deeper in the skin than chickenpox bumps, are hard to the touch, and they are tough to break.

What should you do if you think you may have smallpox?

Your doctor or the public health department will instruct you to limit contact with others. If you have smallpox, symptoms will appear in 7 to 19 days after exposure. People should stay at home and monitor themselves daily for a temperature higher that 101oF (38oC). Immediately contact your local health department to receive guidance on how to isolate yourself (either at home or a designated care site) to minimize the risk of exposure to others. Public health authorities will discuss with you the need for vaccination.

How can we stop the spread of smallpox after someone comes down with it?

Patients will be placed away from others so that they will not continue to spread the virus. In addition, people who have come into close contact with smallpox patients will be notified to receive a vaccination and to be closely watched for symptoms of smallpox. If the vaccine is given within four days after exposure to smallpox, it can lessen the severity of illness or even prevent it. Vaccine and isolation are the strategies for stopping the spread of smallpox.

Is there any treatment for smallpox?

There is no proven treatment for smallpox. Patients with smallpox can benefit from supportive therapy, such as intravenous fluids, medicine to control fever or pain, and antibiotics for any bacterial infections that may develop.
Is smallpox fatal?

Most patients who have smallpox get better, but death may occur in up to 30% of cases. For people exposed to smallpox, the vaccine can lessen the severity or even prevent illness if it is given within four days after exposure. Vaccine administered after exposure has been shown to provide significant protection against death from smallpox. 

Will antibiotics protect me against smallpox?

No. Smallpox is caused by a virus. Antibiotics will not fight the smallpox infection. Getting the vaccine within a few days of exposure to the virus may lessen the severity or prevent disease.

What is the smallpox vaccine, and is it recommended?

The vaccine against smallpox is made with a live virus related to the smallpox virus called vaccinia virus. It is not made with the smallpox virus. Without any known cases of naturally-occurring smallpox, it is not recommended because the risks from the current vaccine outweigh the risk of getting the disease.

If I am concerned about a smallpox attack, can I go to my doctor and request the smallpox vaccine?

In the United States, routine vaccination against smallpox ended in 1972 when the disease was fully controlled. The vaccine is not recommended for routine use. The CDC maintains an emergency supply of vaccine.

If people got the vaccination in the past when it was used routinely, will they be immune?

Not necessarily, since the level of immunity, if any, among persons who were vaccinated before 1972 is uncertain. These persons are assumed to be at risk because it is not known how long immunity lasts. This means that nearly the entire U.S. population has partial immunity at best. Immunity can be boosted effectively with a single revaccination. If you have had smallpox before, you have lifelong immunity.

What is Michigan doing to prepare for a smallpox outbreak?

The Michigan Department of Health and Human Services works closely with physicians and laboratories to make them aware of the signs and symptoms of smallpox and to be able to identify smallpox. Increased surveillance by local health departments is incredibly important in our efforts to detect bioterrorism, investigate potential cases and ensure that patients will be cared for properly with minimal risk to other individuals. Hospitals, health care providers, and health departments throughout the state are prepared to follow the protocols and recommendations for care set by the Centers for Disease Control and Prevention to ensure patient safety.

For more information on smallpox and smallpox vaccination:

Visit The Centers for Disease Control and Prevention (CDC) Smallpox webpage at