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Smallpox as a biologic weapon

Smallpox as a biologic weapon

Smallpox (variola) is classified as a DNA virus. This virus has an incubation

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period of approximately 12 days. It is highly contagious and is transmitted through direct contact with infected individuals through their clothing or linens, or by droplets from person to person but only after the febrile episode has subsided and the onset of rashes has begun.

Smallpox when used as a biologic weapon to inflict mass casualties and injuries has approximately 30% case-fatality rate (the likelihood of fatality per case diagnosed). This figure is doubled when  the virus  is used in aerosol form and  is predicted to result in widespread dissemination affecting several hundreds to thousands in a targeted community.

 

What is smallpox?

According to the World Health Organization (WHO), smallpox was declared eradicated in 1977 and stopped worldwide vaccination by 1980. In the United States, the last child to have been vaccinated was in 1972. Therefore, a large portion of the present population has not immunity to the smallpox virus. A smallpox vaccination plan was introduced in 2003 that included proposals that a designated number of emergency department staff and personnel would receive a smallpox vaccination to ensure that hospital workers especially those working in the ED are immunized in the unlikely event that a smallpox outbreak occurs.  Mass Vaccination is currently under consideration to eliminate the possibility use by terrorist groups as a biologic weapon for offense.

Smallpox was used as a biologic warfare agent as far as the French and Indian war in 1754-1767, when blankets used by smallpox patients were sent into the Indian camps, resulting in more that 50% fatality rate. This was made possible due to the viruses’ high survivability rate in cool and low humidity environments wherein the virus can survive as long as 24 hours even when exposed to the elements.

 

Clinical manifestations of smallpox

Signs and symptoms of smallpox include; high fever, malaise, headache, backache, and prostration. After 1-2 days of the onset of initial signs and symptoms, a maculopopular rash appears on the face, mouth, pharynx and forearms. Only then will the rash progress to the thoracic and trunk region which later turns into vesicular and pustular in form.  There are two major forms of smallpox namely variola major and variola minor. The former is more common and results in higher febrile episodes and more extensive rashes which has a 30% case-fatality rate. Hemorrhagic smallpox, a subtype of variola major, includes the above mentioned signs and symptoms plus bleeding of the mucous membranes resulting in death by the 5th and 6th day following the  initial onset of symptoms.

 

Treatment of Smallpox       

Treatment modalities include supportive care with antibiotics (for any additional infection secondary to the viral infection). The patient must be isolated with the use of transmission precautions. Laundry and biological wastes should be properly decontaminated, autoclaved or properly disposed when necessary to avoid the spread of the virus. All persons who have household contact with the patient after the onset of the fever should be vaccinated within four days to prevent infection. A patient with a body temperature of 38 degrees Celsius must be placed in isolation. Deaths resulting from smallpox infection should be cremated since the virus can survive in the scabs for a very long period of time.

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