As suggested by its name, the JC Virus DNA PCR is used to diagnose the JC Virus. The JC Virus is also known as the John Cunningham Virus. A few decades ago, it was known as Papovavirus. The virus is genetically alike SV40 and the BK Virus. The virus causes a wide range of diseases like PML and immunodeficiency. People infected by this virus lose their ability to fight infections Polymerase Chain Reaction (PCR) is a technique used to detect JC Virus. It uses small amounts of DNA to test for signs of the infection. The test amplifies or generates copies of a specific sequence and determines the chances of an infection.