Laboratory diagnosis to differentiate smallpox, vaccinia, and other vesicular/pustular illnesses.

Abbreviations: APHL Association of Public Health Laboratories; BSL biosafety level; CA chorioallantoic membrane; CDC Centers for Disease Control and Prevention; DFA direct fluorescent antibody; EM electron microscopy; FBI Federal Bureau of Investigation; HSV herpes simplex virus; LRN Laboratory Response Network; PCR polymerase chain reaction; USAMRIID US Army Medical Research Institute of Infectious Diseases; VZV varicella-zoster virus