| jc virus excreted by multiple sclerosis patients and paired controls from hungary. | jc virus (jcv), a human polyomavirus, is the agent of the demyelinating disease progressive multifocal leukoencephalopathy (pml). jcv exists in four main genotypes in the usa. type 1, including subtypes type 1a and type 1b, makes up about 64% of strains in the usa and is thought to be of european origin. type 2 is found in asia, and type 3 in africa. a fourth type is found only in the usa. in general, these genotypes differ in 1-2.5% of their dna sequence. thirty ms patients and 30 paired contro ... | 1998 | 9599332 |