Polymerase chain reaction analysis of the patient's isolate, compared with wild strains and vaccine strains of VZV. The polymerase chain reaction products are separated by gel electrophoresis. Lane 1 is the Oka vaccine strain; lane 2, a US wild strain (Emily); lane 3, the isolate from the sibling who developed varicella. The Oka strain and the isolate both have changes in the bases in the region wherePstI digests the wild type virus. Thus,PstI is unable to digest the vaccine or isolate, so there is only a single 349-kb band. The wild strain, which contains thePstI site, is split into 2 fragments, both of which are smaller (99 kb and 250 kb) than the single nonsplit fragment from the Oka or isolate strains.