You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Progressive multifocal leukoencephalopathy is caused by and explain in detail?
(D) Papova virus # Progressive multifocal leukoencephalopathy is a viral encephalitis caused by a polyomavirus (Papova virus or JC virus, totally unrelated to Creutzfeldt-Jakob disease) because the virus preferentially infects oligodendrocytes, demyelination is its principal pathologic effect.> Progressive multifocal leukoencephalopathy (PML), also known as progressive multifocal leukoencephalitis, is a rare and usually fatal viral disease that is characterized by progressive damage (-pathy) or inflammation (-His) of the white matter (leuko-) of the brain (-encephalo-) at multiple locations (multifocal).> It occurs almost exclusively in people with severe immune deficiency, e.g. transplant patients on immunosuppressive medications, or AIDS patients.> The cause of PML is a type of polyomavirus called the JC virus (JCV).