Biological Weapons -- Smallpox

Smallpox poses a serious bioterrorist threat because it has a high fatality rate, spreads easily in any climate and season, is highly infectious by aerosol, is environmentally stable, and can retain infectivity for long periods. Additionally, the majority of the US population has no immunity, little vaccine is readily available, and no effective treatment exists for the disease. For those who don't die from the disease, they usually experience severe scarring. Russia still possesses an industrial facility capable of producing tons of smallpox virus annually and maintains a research program thought to be seeking to produce more virulent and contagious strains. In theory, the only other repository for smallpox is in Atlanta, Georgia. An aerosol release of smallpox virus would disseminate readily given its considerable stability in aerosol form and epidemiological evidence suggesting the infectious dose is very small. Even as few as 50-100 cases would likely generate widespread concern or panic and a need to invoke large-scale, perhaps national emergency control measures. . Symptoms After a 7 - 17-day incubation period, symptoms begin acutely with high fever, headache, chills, malaise, muscle pain, vomiting, abdominal and back pain. During the initial phase, 15% of patients become delirious 2-3 days later, lesions appear which quickly change into pus-filled blisters especially on the extremities and face. Patients are most infectious 3-6 days after the onset of fever. Virus is shed from the scabs and respiratory secretions. How does it spread? Smallpox spreads directly from person to person, primarily by spray expelled from the back of the mouth of an infected person or by aerosol. Contaminated clothing or bed linen can also spread the virus. Special precautions need to be taken to insure that all bedding and clothing of patients are autoclaved. Disinfectants such as hypochlorite and quaternary ammonia should be used for washing contaminated surfaces. Diagnosis Smallpox is usually diagnosed after looking at blister scrapings under an electron microscope. Sometimes a modified silver stain is used; however, these tests can't distinguish between smallpox, monkeypox or cowpox. Smallpox is differentiated from chicken pox by the centrifugal distribution of its rash and the presence of lesions at the same stage of development everywhere on the body. Treatment Strict quarantine with respiratory isolation for 17 days is applied to all people in direct contact with the index case or cases. People exposed to either weaponized smallpox or clinical cases must be vaccinated immediately. It's effective at lessening or preventing illness if done within a few days of exposure. Vaccinia immune globulin (VIG) is given to patients who cannot take the vaccine - like those with impaired immune systems, HIV infection, are pregnant, have a history or evidence of eczema OR, current household, sexual, or other close physical contact with person(s) possessing one of these conditions. Specifics on treatment can be found here Vaccine No one in the U.S. has been vaccinated for the past 25 years. Vaccination ceased in this country in 1972. Anyone who was vaccinated before that time no longer has immunity. Vaccination with a verified clinical "take" (vesicle with scar formation) within the past 3 years is considered immune to smallpox. Smallpox vaccine (a weakened form of the virus) is administered which results in a permanent scar. A blister usually appears 5-7 days after inoculation which scabs over and heals over the next 1-2 weeks. Reactions include low-grade fever and enlarged lymph nodes. Vaccinia immune globulin (VIG) can be obtained from the CDC and is administered at a dose of 0.6 mL/kg IM. Mortality Two types of smallpox generally are recognized. Variola major, the most severe form, has a fatality rate of 30% in unvaccinated individuals and 3% in those previously vaccinated. Variola minor, a milder form of smallpox, is lethal in only 1% of unvaccinated individuals. Sources: CDC; http://www.bt.cdc.gov/ Federation of American Scientists; http://www.fas.org/nuke/intro/bw/agent.htm USAMRIID's Medical Management of Biological Casualties Handbood; Fourth Edition February 2001; pages 9-10; http://usamriid.detrick.army.mil/education/bluebook/bluebook.pdf

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