infectious diseases
Smallpox
Diagnosis of Smallpox
Polymerase chain reaction (PCR) Electron microscopy Unless laboratory exposure is documented or an outbreak (due to bioterrorism) is suspected, only patients that fit the clinical case definition for smallpox should be tested because of the risk that test results may be falsely positive. An algorithm for evaluating the risk of smallpox in patients with fever and rash is available on the CDC web site (CDC Algorithm Poster for Evaluation of Suspected Smallpox). Diagnosis of smallpox is confirmed by documenting the presence of variola DNA by PCR of vesicular or pustular samples. Or the virus can be identified by electron microscopy or viral culture of material scraped from skin lesions and subsequently confirmed by PCR. Suspected smallpox must be reported immediately to local public health agencies or the CDC at 770-488-7100. These agencies then arrange for testing in a laboratory with high-level containment capability (biosafety level 4). Point-of-care antigen detection assays are being developed. 