Emergency Preparedness

Kern Medical Bioterrorism Response Guide Section 2-C-1 – Smallpox

marrow is believed to lead to defective blood coagulation. A high level of viremia is maintained in this type of smallpox. The incubation period may be shorter with more severe prodromal symptoms. Soon after the onset of illness, the patient develops a dusky erythema followed by petechiae and bleeding from the conjunctiva and mucous membranes. Death generally occurs about the 6 th day of the rash often before lesions characteristic for smallpox rash develop. There are two forms of hemorrhagic-type smallpox, early and late. These forms are differentiated by the occurrence of hemorrhages after the appearance of the rash in the late form. Hemorrhagic-type smallpox occurs among all ages and in both sexes but is more common in adults. Pregnant women seem more susceptible to developing this type of smallpox. Differential diagnosis includes meningococcemia and acute leukemia. Modified-type Presentation This form of smallpox generally occurs in previously vaccinated persons. The modification relates to the character and development of the rash with more rapid progression and resolution of the lesions. The prodromal stage is similar to typical smallpox however the duration of prodrome may be shorter and fever may be lower or in some cases absent. Once the lesions begin to appear, they generally evolve more quickly with crusting completed by 10 days. The lesions may be fewer in number and more superficial than those seen with ordinary smallpox. Diagnosis Tentative diagnosis is based on the characteristic rash and other symptoms. The usual method of diagnosis is the demonstration of virions on electronic microscopy from vesicular scrapings. Initial laboratory confirmation should not be attempted in clinical laboratories . Differential Diagnosis The differential diagnoses include chicken pox, allergic contact dermatitis, erythema multiforme with bullae, secondary syphilis, and atypical measles. Chickenpox eruptions are generally more numerous on the trunk than on the face and extremities and lesions occur in crops that are in different stages of development.

Treatment There is no known antiviral therapy. The only therapy known to date is supportive and includes hydration and medication for fever and pain. Sedation may help the patient to rest more comfortably. Antibiotics should only be prescribed for secondary skin infections.

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