JC virus is a ubiquitous human polyomavirus present in populations worldwide. Seven genotypes differing in DNA sequence by approximately 1-3% characterize three Old World population groups (African, European and Asian) as well as Oceania. It is possible to follow Old World populations into the New World by the JC virus genotypes they carried. The first population to settle in the Americas, the Native Americans, brought with them type 2A from northeast Asia. European settlers arriving after Columbus carried primarily type 1 and type 4. Africans brought by the slave trade carried type 3 and type 6.