Description
Human polyomavirus 2, commonly referred to as the JC virus or John Cunningham virus, is a type of human polyomavirus (formerly known as papovavirus).
The virus causes PML and other diseases only in cases of immunodeficiency, as in AIDS or during treatment with drugs intended to induce a state of immunosuppression.
The initial site of infection may be the tonsils, or possibly the gastrointestinal tract, where the virus remains latent.