the centers for disease control and prevention considers a person with jcv infection laboratory-confirmed if: jcv isolated from or jcv-specific antigen or genomic sequences detected in tissue, blood, cerebrospinal fluid, or other body fluids; 2) equal or more than 4-fold change in jcv-specific neutralizing antibody titers between acute and convalescent samples; or 3) jcv or lacv igm antibodies in serum with jcv-specific neutralizing antibodies equal or more than 4-fold higher than lacv-specific neutralizing antibody titers in the same specimen or a later specimen.