The most important step in confirming a case of smallpox is laboratory diagnosis. Someone who has recently been vaccinated and who wears gloves and a mask must collect the specimens. To obtain vesicular or pustular fluid, it is often necessary to open lesions with the blunt edge of a scalpel. The fluid can then be harvested on a cotton swab. Scabs can be picked off with forceps. Specimens should be deposited in a primary sterile vacutainer tube sealed with tape, packed with absorbent padding in a secondary "screw-top" container and then in a United Nations approved shipping carton, in accordance with 49CFR172. See www.iata.org and www.dot.org for additional information on shipment of diagnostic specimens and etiologic agents.

As always, state or local health department laboratories should immediately be contacted regarding the shipping of specimens. Laboratory examination and diagnosis requires high-containment (Biosafety Level-4) facilities and should be undertaken only in designated laboratories where appropriately trained personnel and equipment are available.

Smallpox infection can be rapidly confirmed in the laboratory by electron microscopic examination of vesicular or pustular liquid or scabs. Definitive laboratory identification and characterization of the virus involves growth of the virus in the cell culture or on chorioallantoic egg membrane and characterization of strains by use of biologic assays, including the polymerase chain reaction (PCR), restriction fragment-length polymorphism analysis (RFLP) and ELISA. Confirmation using these methods can be accomplished in a few hours.

Contents: Smallpox (Extensive Information)             

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