- Smallpox disease is caused by the variola virus, which is acquired through air droplets, direct contact with skin lesions, or objects contaminated by an infected person.
- Naturally occurring smallpox was eradicated in 1977. Travelers are not at risk unless a bio-terrorism event occurs.
- Symptoms include fever, muscle aches, fatigue, headache, and backache, followed by a rash (on the face, hands, forearms, and trunk), progressing to blisters, pus, and scabs.
- Consequences of infection include death in 30% of cases; no effective treatment is available.
- Prevention includes strict infection control measures in lab workers and those exposed during a smallpox event.
- Smallpox vaccine is available only to the military, researchers, and certain first responders and is given as a single-dose using a special needle.
- Vaccine side effects include fever and local reactions severe enough to cause absenteeism in up to one-third of vaccinees. Severe reactions include myocarditis, generalized spread of the virus in the bloodstream or to the brain, and a life-threatening rash.
- Duration of vaccine protection is about 5 to 10 years. Boosters are recommended for certain at-risk groups at intervals that vary according to exposure risk.
Smallpox is a highly contagious (sometimes fatal) disease caused by the variola virus. Humans are the only natural hosts.
Naturally occurring smallpox was declared as eradicated in 1980 after a worldwide vaccination program. After the disease was eliminated, routine vaccination of the general public was halted, and vaccine was given only to military personnel (until 1990) and travelers going to infected areas (until 1982). Very few people today would be expected to have residual immunity from earlier vaccination. Smallpox vaccine is currently utilized only by the military, first responders, and some laboratory personnel who work with the vaccinia virus used in the vaccine.
Naturally occurring smallpox has been eradicated.
The disease is spread person-to-person by inhalation of air droplets or direct contact with skin lesions or objects contaminated by an infected person.
Transmission can also occur from contact with the virus in a laboratory setting. Rarely, smallpox has been spread by exposure to an aerosol release of the virus, such as in enclosed buildings, buses, or trains.
Travelers are not at risk unless a bio-terrorism event occurs.
Persons who may be at risk include military personnel, first responders, laboratory workers who work with the vaccinia virus, persons who work with animals contaminated or infected with these viruses, and health care workers who are involved in clinical trials or who are predesignated to care for smallpox cases in the event they occur.
Following an incubation period of 12 to 14 days (range: 7-17 days), initial symptoms include fever, muscle aches, exhaustion, severe headache, and backache, followed by the appearance of a rash 2 to 4 days later. A flat red rash appears and progresses to raised bumps, blisters, pustules, and scabs. The rash appears first on the face and forearms, spreads to the trunk and legs, and frequently involves the palms and soles.
Consequences of Infection
Smallpox is fatal in approximately 30% of cases; no effective medical treatment exists.
Need for Medical Assistance
Persons who may have been exposed to smallpox (variola) virus should seek immediate medical attention.
Nonvaccine: Persons who work with the virus or who may have been exposed during release events should observe strict infection-control measures.
Vaccine: Several effective vaccines are available; all are live-virus vaccines containing vaccinia virus. The vaccine does not contain variola (smallpox) virus.
Smallpox vaccine and immune globulin are stockpiled and controlled by national governments. In the U.S., smallpox vaccine is not commercially available to health care providers, but the U.S. government has sufficient quantities of the vaccine to inoculate every person in the country in an emergency. If needed, the vaccine would be distributed by CDC.
- Vaccination within 3 days of exposure can significantly reduce symptoms or prevent smallpox disease.
- Vaccination 4 to 7 days after exposure may decrease the severity of disease.
- Vaccination will not protect infected persons who have already developed a rash.
Vaccination consists of a single dose given with a 2-pronged needle that is used to repeatedly puncture the skin on the arm. The person vaccinated must return to the health care provider 6 to 8 days after vaccination to determine whether vaccination was successful.
After primary vaccination, protection against smallpox is likely to persist for 5 to 10 years.
Revaccination is routinely recommended for:
- Certain laboratory workers
- Persons who administer smallpox vaccine
- U.S. military personnel (may be required)
- Designated first responders
In the event of a credible smallpox threat or outbreak, "out-the-door" revaccination is recommended for:
- Civilian first responders (i.e., previously vaccinated public health and health care volunteers in the U.S. Civilian Smallpox Preparedness and Response Program).
- Persons administering the vaccine, regardless of interval since last dose.
Travel: Smallpox vaccine is not recommended for international travel unless otherwise indicated.
Adverse effects include fever and local reactions severe enough to cause absenteeism in up to one-third of vaccinees. These include sore arm with redness, itching, pain, or swelling at the injection site; swollen, tender lymph nodes in the armpit; low-grade fever with headache, muscle aches, nausea, or fatigue. Severe reactions include myocarditis, generalized spread of the virus in the bloodstream or to the brain, and a life-threatening rash.
Those with underlying illness or compromised immunity should not receive smallpox vaccine. Speak to your health care provider for any concerns about this vaccine.
When indicated, 1 dose is given.
- Timing of revaccination (if needed) depends on the level of risk; some persons are revaccinated every 3 years (lab workers) or 10 years (vaccine administrators) and first-responders on an “out the door” basis when a smallpox outbreak or risk of an outbreak exists.
Care of the Vaccination Site
- Cover with sterile gauze after inoculation; keep the site clean and dry to avoid infection and prevent transmission to other parts of the body or to other people.
- Apply povidone-iodine ointment to the vaccination site (every 1-3 days starting on day 7 after vaccination) to minimize the risk of transmission.
- Wear a long-sleeved shirt over the gauze-covered site.
- Do not scratch or rub the site.
- Change the dressing every 1 to 2 days (or if it becomes wet).
- Carefully discard any gauze in plastic bags.
- Wash hands thoroughly with soap and water or with disinfecting agents after any contact with the site, the gauze dressing, or materials that have come in contact with the site (clothing, bedding, etc.).
- Clothing or bedding that comes into contact with the site should be laundered in hot water.