Editing Progressive multifocal leukoencephalopathy (section)

===JC virus infection===
The cause of PML is a type of [[polyomavirus]] called the [[JC virus]] (JCV), after the initials of the person (John Cunningham) from whose tissue the virus was first successfully cultured. Publications indicate 39<ref>{{cite journal|doi=10.1371/journal.ppat.1000363|title=Seroepidemiology of Human Polyomaviruses|year=2009|editor1-last=Atwood|editor1-first=Walter J.|last1=Kean|first1=Jaime M.|last2=Rao|first2=Suchitra|last3=Wang|first3=Michael|last4=Garcea|first4=Robert L.|journal=PLOS Pathogens|volume=5|issue=3|pages=e1000363|pmid=19325891|pmc=2655709 |doi-access=free }}</ref> to 58%<ref>{{cite journal|doi=10.1086/597126|title=Prevalence of Polyomavirus BK and JC Infection and Replication in 400 Healthy Blood Donors|year=2009|last1=Egli|first1=Adrian|last2=Infanti|first2=Laura|last3=Dumoulin|first3=Alexis|last4=Buser|first4=Andreas|last5=Samaridis|first5=Jacqueline|last6=Stebler|first6=Christine|last7=Gosert|first7=Rainer|last8=Hirsch|first8=Hans H.|journal=The Journal of Infectious Diseases|volume=199|issue=6|pages=837–46|pmid=19434930|doi-access=free}}</ref> of the general population are seropositive for antibodies to JCV, indicating current or previous infection with the virus. Other publications put the percentage at 70 to 90% of the general population.<ref name="shakel">{{cite journal|author1=Laura A. Shackelton |author2=Andrew Rambaut |author2-link=Andrew Rambaut |author3=Oliver G. Pybus |author4=Edward C. Holmes |year=2006|title=JC Virus evolution and its association with human populations|journal=Journal of Virology|volume=80|issue=20|pages=9928–9933 |doi=10.1128/JVI.00441-06|pmc=1617318|pmid=17005670}}</ref> JCV causes persistent asymptomatic infection in about one-third of the adult population, based on viral shedding into the urine from the site of asymptomatic infection in the kidney. The virus causes disease only when the immune system has been severely weakened.<ref>{{Cite journal |last1=Cortese |first1=Irene |last2=Reich |first2=Daniel S. |last3=Nath |first3=Avindra |date=January 2021 |title=Progressive multifocal leukoencephalopathy and the spectrum of JC virus-related disease |journal=Nature Reviews Neurology |language=en |volume=17 |issue=1 |pages=37–51 |doi=10.1038/s41582-020-00427-y |pmid=33219338 |pmc=7678594 |issn=1759-4766}}</ref>