Bioterrorism/Disease

Information About Smallpox

Agent, clinical disease, and incubation period

Smallpox is caused by infection with the variola major virus. The clinical syndrome of smallpox begins with a brief prodomal illness of fever, headache, backache, and myalgias, followed quickly by the appearance of a maculopapular rash. The rash appears first on the face and forearms, including the tongue and roof of the mouth, extending afterwards to the legs, palms, soles and trunk. Smallpox is distinguished from chickenpox by the more prominent involvement of the face and extremities (as compared to the trunk in chickenpox), the involvement of palms and soles (uncommon in chickenpox) and the fact that the lesions in any given area of the skin are all of the same morphology in smallpox (as opposed to crops of lesions in different stages in chickenpox). The incubation period for smallpox is 7-17 days. Patients are infectious at the time of onset of the rash. If a physician suspects a bioterrorism-related illness, please notify immediately Infectious Diseases, Infection Control or the appropriate public health authorities.

Precautions

Smallpox is spread person-to-person by droplets, droplet nuclei, and direct contact with infected skin lesions. Patients with suspected smallpox should be placed in a negative pressure room on airborne and contact precautions. Patients are infectious for approximately three weeks or until all lesions have scabbed over. A mask should be put on a patient with smallpox if they must leave a negative pressure room.

Actions in the Event of a Suspected Exposure

Since this is such a highly communicable disease, quick identification and proper diagnosis for the first occurring cases is critical. Hospitals, emergency room facilities and physicians need to have an awareness of the early symptoms (and the differences from other common rash like illnesses). Hospital systems routinely monitor emergency visits and are vigilant for any unusual medical occurrence or clusters of specific symptoms. Diagnosed patients would be hospitalized using strict isolation precautions (respiratory, skin contact) to prevent spread. In addition, people who have come into close contact with smallpox patients should be vaccinated immediately and closely watched for symptoms of smallpox.

Treatment

There is currently no known effective antiviral treatment for patients infected with small pox. Supportive care includes intravenous fluids, medicine to control fever and pain, and antibiotics for secondary infections that may develop. Available experimental medication has potentially significant side effects and is not appropriate for prophylaxis.

Is There a Vaccine?

Routine vaccination against smallpox was discontinued in 1972 and the previously available smallpox vaccine was removed from the commercial market in 1983. Because few people 29 years of age have been vaccinated, and the long-term effectiveness of those persons vaccinated before 1972 is uncertain, it is generally assumed that the entire US population is susceptible to small pox. At present, there is an insufficient supply of vaccine to recommend routine vaccination of the public and or healthcare workers. Vaccination within 3-4 days following smallpox exposure can prevent the disease in many people and prevent death in most. At present smallpox vaccine is supplied only to certain laboratory workers at risk of infection. The Federal Government has recently announced plans to greatly step up production of small pox vaccine (approximately 300 million doses) within the next year. However, no widespread routine vaccination program is currently planned.