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What is smallpox?Smallpox is a virus that used to cause one of the most feared illnesses in history. A global World Health Organization vaccination program from the mid-1960s to 1980 successfully eradicated smallpox from the face of the earth. The last naturally occurring case of the disease occurred in 1977 in Somalia. Smallpox virus is still maintained in high-security government laboratories within at least two countries: the United States and Russia. Though less contagious than influenza and chickenpox, single cases introduced into a population could result in large epidemics. Since most persons living today do not have any immunity to the virus, it is possible that any re-introduction of smallpox could result in a global pandemic.
Since smallpox has been eradicated, why has it become a health concern in the United States?
Even though it has been officially eradicated, smallpox virus still is maintained in high-security government laboratories within at least two countries: the United States and Russia. Federal government national security experts have expressed concerns that some countries or terrorist groups might acquire smallpox virus that could be used against the United States. In the weeks prior to the invasion of Iraq in 2003, the federal government implemented an ambitious smallpox vaccination program that targeted healthcare workers. Only a small proportion of the campaign’s vaccination goals were met.
What are the symptoms of smallpox?
When smallpox naturally occurred, symptoms usually developed 12 to 14 days after exposure to another person with smallpox and included high fever, severe body aches, vomiting, and a rash. The often painful rash usually appeared 2 to 3 days after the fever and occurred first on the face, mouth, hands, forearms, palms, or soles of the feet, spreading from there to the legs and the trunk. The rash would change to raised bumps and then pus-filled blisters over the course of a week. After about 3 weeks, the blisters would crust, scab, and fall off, often leaving a pitted scar.
Is smallpox fatal?
When smallpox occurred in the past, most patients recovered, though up to 30 percent of smallpox cases died from the disease.
How is smallpox spread?
Smallpox is spread person-to-person in two ways. A person can inhale particles containing the virus that have been coughed into the air by an infected person, or a person can be infected when touching the rash or blisters of an infected person and then touching their own nose or mouth. Contact with the clothing and bedding of an infected patient can also spread the virus.
Is smallpox contagious?
Yes. Smallpox can be spread from person to person. It can be spread through the air (e.g., by coughing or sneezing) and by body contact, or from contact with clothing or bedding that has been touched by an infected person. Smallpox is contagious after an infected person has developed a fever and rash. Smallpox patients are usually contagious until the scabs from the rash fall off. Individuals with smallpox, as well as those who may have been exposed to the virus, should be separated from those who have not yet been exposed.
How contagious is smallpox?
In the past, the chance of an unvaccinated person getting smallpox after being exposed to someone infected with smallpox was 35 percent to 70 percent. In comparison, the chance of a susceptible person getting chickenpox or measles after being exposed to these diseases is 80 percent to 90 percent. Those at greatest risk of getting smallpox would be close, unvaccinated contacts of an infected individual, such as family members or healthcare workers.
How is smallpox diagnosed?
Doctors look for the symptoms of high fever, severe body aches, vomiting and a characteristic rash. Laboratory tests can also be used. Doctors would conduct these tests in conjunction with DOHMH and the U.S. Centers for Disease Control and Prevention (CDC).
Is there any treatment for smallpox?
Although there is no known effective treatment for the disease once symptoms occur, vaccination within 3 days after exposure will probably offer some protection from disease or could prevent the disease from becoming more severe. In addition to providing protection, the vaccine against smallpox also can stop the spread of this disease. During previous outbreaks, approximately two-thirds of those infected with smallpox survived.
Some new medications are being tested that might be used to treat smallpox after symptoms have started. Patients with smallpox need fever and pain medications, fluids and antibiotics if bacterial infections occur. Not all persons with smallpox disease would necessarily need to be treated in hospitals, which would be reserved for the most seriously ill patients.
What is smallpox vaccine?
The smallpox vaccine is a live virus vaccine that helps the body protect itself against the smallpox virus. It contains vaccinia virus, which is a different virus than the smallpox virus. The vaccine does not contain the smallpox virus, and cannot give you smallpox disease.
The vaccine is the best way to prevent smallpox disease. It is also the best way to prevent death in someone who has been exposed to the smallpox virus. Vaccination within 3 days after exposure will probably offer some protection from disease or could prevent the disease from becoming more severe.
Is the vaccine available to the general public?
No. The vaccine is not currently available to the general public. In fact, it is not currently recommended for use in the general population because, in the absence of a smallpox case, the risks associated with the vaccine are greater than those associated with the disease itself. However, in the event of a smallpox outbreak, the CDC would quickly provide vaccine to people who might have been exposed to the disease and to those who might be exposed to other persons infected with smallpox. If there were an outbreak of smallpox, the federal government has enough smallpox vaccine for the entire country, if needed.
If someone is exposed to smallpox, is it too late to get a vaccination?
No. An unvaccinated person exposed to the virus should be vaccinated immediately. Vaccination within 3 days after exposure will probably offer some protection from disease or could prevent the disease from becoming more severe.
If I received smallpox vaccine in the past, am I still protected?
Protection against smallpox lasts for about 3 to 5 years. After 5 years, a smallpox vaccination may no longer provide full protection against smallpox. However, someone who has been vaccinated sometime in their lives probably will have a less severe reaction to the smallpox virus than someone who has never been vaccinated. Most people in the United States received smallpox vaccine over 30 years ago or have never been vaccinated. The United States stopped routinely vaccinating the general public with smallpox vaccine in 1972.
How is the smallpox vaccine given?
The vaccine is given using a two-pronged needle. It is dipped into a vaccine solution and then used to quickly prick a small area on the skin for a few seconds. The pricking is not deep, but it will cause a sore spot and a few drops of blood may appear. The vaccine is usually given on the outside of the upper arm.
How do you know if a smallpox vaccination is successful?
If the vaccination is successful, a red and itchy bump will form on the vaccine site in 3 to 4 days. About a week after vaccination, the bump will become a large blister, fill with pus, and then begin to drain. In about 2 weeks, the blister will begin to dry up and a scab will form. The scab usually falls off about 3 weeks after the vaccination, leaving a small scar. When people receive the vaccine for the first time, the possibility of more redness and swelling is greater than for those who have received the vaccine at some other time in their lives.
What are normal side effects of a smallpox vaccination?
The blister and the scab that develop are normal reactions to the vaccine virus. Most people also have some itchiness, pain and swelling at the vaccination site. Other common side effects are: fever, swollen lymph glands, fatigue, headache, nausea, muscle aches, and redness at the vaccine site. In some people, the local swelling and redness can be severe, but this will usually get better on its own. Up to one-third of the people who receive the vaccine may become sick enough to miss some work. Most symptoms occur about one week after vaccination.
Is there the possibility that there could be more serious side effects (bad reactions) from the vaccine?
Yes. There can be serious side effects in some people who receive the smallpox vaccine. Fortunately, these bad reactions are much less common in people who do not have certain health problems or conditions. Severe reactions are also more common among people who receive the smallpox vaccine for the first time compared to persons who had been vaccinated at some other time in their lives. Most severe reactions to the vaccine can be treated. The treatment includes an injection of immune globulin (antibodies) and supportive therapy.
In rare instances, people have had very bad reactions, to the vaccine. Based on past experience, it is estimated that one or two people out of every 1 million people vaccinated may die as a result of reactions to the vaccine. The reactions that require immediate medical attention are:
- Eczema vaccinatum -- a severe skin rash caused by widespread skin infection from the vaccine virus in people with preexisting skin conditions such as eczema or atopic dermatitis.
- Progressive vaccinia (or vaccinia necrosum) -- an ongoing infection of skin at the vaccination site with tissue destruction that can lead to loss of a limb or death in people with immune system problems.
- Post-vaccinial encephalitis -- an inflammation of the brain that can lead to disability or death.
In the past, about 1,000 people in every 1 million people vaccinated for the first time had reactions that were serious, but did not put their lives in danger. These reactions can be more severe in those with compromised immune systems and may require medical attention:
- Spread of the vaccinia virus from the vaccination site -- a rash or outbreak of sores similar to the vaccination blister that appears in one area of the body. This is caused when the unhealed vaccination site is touched and then contact is made with another part of the body or another person. It usually occurs on areas of the body that are more frequently touched, such as the genitals or face. If it occurs in the eyes, it can damage sight or lead to blindness. Most skin lesions will heal without any special treatment. Washing hands with soap and water after touching the vaccine site or the used (dirty) bandages will help prevent this.
- Generalized vaccinia -- a widespread rash that spreads from the vaccination site through the blood. Fluid-filled or pus-filled sores break out on parts of the body away from the vaccination site (usually on the chest or abdomen). This condition usually disappears without any special treatment.
- Erythema multiforme -- an allergic rash that appears in response to the vaccine. It can take various forms such as red spots, bumps, or hives and can lead to secondary skin infections, which are usually treatable.
People with certain medical conditions are more likely to have these reactions. They include people with weakened immune systems or certain skin conditions. These people should not get the smallpox vaccine unless they have been exposed to smallpox.
The smallpox vaccine contains a live virus, vaccinia. Can this live virus in the vaccination site be spread to other persons?
Yes. The virus in the smallpox vaccine is present at the site of the vaccination until it is completely healed and the scab falls off (about 3 weeks). Because the vaccine site contains a live virus, it can be spread to other people and other parts of the body. This can usually be prevented by not touching the vaccine site. Proper care of the vaccine site includes covering the site with the recommended dressing, carefully washing your hands after touching the site or the dressing, and disposing of used dressing materials in sealed or zip-locked plastic bags.
What are pre-existing health problems and conditions that might cause more severe side effects from the smallpox vaccine?
There are certain health problems that may put you or your close physical contacts at higher risk for a severe side effect from the vaccine. Anyone who has ANY of the following health conditions, or lives with or has close physical or sexual contact with someone with ANY of these conditions, would be advised NOT to get vaccinated (unless there is a smallpox outbreak, in which the risk of smallpox infection may be greater than risk of the vaccine):
- Weakened or compromised immune systems. This includes persons with HIV infection or AIDS, cancer, leukemia, lymphoma, organ transplants, autoimmune diseases (like lupus), or problems producing antibodies (for example, the disease agammaglobulinemia, which is when a person lacks normal antibodies) or persons being treated with chemotherapy, radiation therapy, high dose steroids (such as oral prednisone for more than 2 weeks) or other medicines that weaken the immune system. However, if someone is a cancer survivor and (a) their cancer is cured, (b) they are no longer on chemotherapy or radiation therapy and (c) their doctor feels their immune system is normal and no longer weakened, it is okay to get the smallpox vaccine. If you have any concerns about your health history, talk with your doctor.
- A history of EVER having the skin diseases eczema or atopic dermatitis (Persons who have ever had a skin problem that caused them to have red, patchy, scaly, itchy skin for more than 2 weeks that was not due to another cause, especially if this skin problem tended to come and go, may have had eczema or atopic dermatitis). Ask your doctor if you are not sure whether you have ever had eczema or atopic dermatitis.
- Any currently active skin diseases that cause breaks in the normal barrier of the skin, such as burns, psoriasis, shingles, an allergic rash, impetigo or severe acne.
- Women who are pregnant or who will be trying to get pregnant in the four weeks after vaccination.
- A cardiac condition with or without symptoms: known coronary disease including previous myocardial infarction, angina; congestive heart failure, cardiomyopathy, stroke or transient ischemic attack, chest pain or shortness of breath or other heart condition under the care of a doctor.
Children younger than a year may be at higher risk for severe reactions (especially encephalitis) if they are exposed to vaccinia virus in the smallpox vaccine. Although the CDC does not currently list it as a reason not to be vaccinated, the New York City Department of Health and Mental Hygiene recommends that persons who live with a child younger than one year of age consider not getting vaccinated at this time, since it is difficult to avoid close contact when caring for an infant.
In addition to the health conditions listed above, persons who have any of the following health problems or conditions themselves should NOT get the smallpox vaccine:
- Women who are breastfeeding
- Anyone who is ill at the time they are supposed to be vaccinated
- Anyone who is using steroid eye drops, and
- Anyone with allergies to one of the ingredients in the vaccine (polymyxin B, streptomycin, chlortetracycline, or neomycin) or with a severe allergy to latex (anaphylaxis reaction, including severe swelling, hives or difficulty breathing)
- Anyone with 3 or more of the following cardiac risk factors: hypertension, high cholesterol, diabetes, first degree relative who had a heart condition before the age of 50, or currently smokes cigarettes.
You may need to speak to your doctor to review your medical history to be sure it is okay to get the smallpox vaccine. Also, before you decide to get the vaccine, you should talk to your household and other close contacts to be sure they do not have any medical problems that are listed above. They may need to talk to their doctor to be sure that they do not have any of these health problems or conditions.
Are there any risks to my pets if I get the smallpox vaccine?
Smallpox is a disease of humans. However, the vaccinia virus used in the vaccine can infect animals. While dogs have a very low risk of any reaction if they accidentally touch the vaccinia virus in the vaccination site (including the scab), some animals, such as hamsters, may be more likely to have a reaction to an exposure. The best way to avoid a problem is to protect your pets from any possible contact with the vaccinia virus during the 3 week period after you have been vaccinated. Until it completely heals, you should keep the vaccination site bandaged and covered with long-sleeve clothing at all times, including while you sleep.
If you have pets or contact with other animals, here are some other ways to minimize their risk while your vaccination site heals.
- Do not let animals sniff or have any direct contact with the vaccination site or the bandages, clothing or sheets that touch the scab.
- Keep pets out of the room when you are changing bandages or changing clothes.
- Before allowing your pet back into the room after you have changed your bandage, carefully disinfect the bandage with bleach, dispose of it in a sealed plastic bag, put any clothing that had contact with your vaccination site in the laundry and wash your hands well.
- Make sure that pets and rodents do not have access to trash containers that have contaminated bandages in them. Cover trash containers tightly, and take them to an inaccessible area.
- Make sure that your vaccination site is bandaged and your hands are washed before handling "pocket pets" such as guinea pigs, hamsters and other rodents. Do not allow them to touch the skin area around your bandage.
- Wildlife biologists should consider avoiding handling and releasing live rodents for about three weeks after being vaccinated, or until their scab falls off.
- If your animal has any unusual symptoms, and it could have been exposed to vaccinia virus accidentally, contact the health department and your veterinarian.
What might we expect if an outbreak of smallpox occurred today?
In the event of a smallpox outbreak, The New York City Health Department would rapidly identify and isolate people with smallpox, identify people who have had close contact with infected patients and quickly vaccinate them. Mass vaccination might be considered depending on the size of the outbreak.
What is New York City doing to prepare for a potential smallpox outbreak?
Every day, The New York City Health Department monitors disease trends, emergency department visits, and 911 calls that might signify that a bioterrorist attack has occurred. The New York City Health Department also educates doctors and prepares internally to rapidly evaluate suspected bioterrorism-related illnesses.
The New York City Health Department has developed a smallpox response plan with other city, state and federal agencies in the event that smallpox were detected anywhere in the world, including in New York City. Smallpox vaccination would be made available to New Yorkers if there was an outbreak of smallpox in New York City.
For more information about smallpox, visit the CDC's website
Last Updated: December 2011