It was discovered in 2007 in stored samples of human respiratory secretions collected by the Karolinska Institute, after which the virus is named.

[1] The prevalence of KI virus as detected by the presence of its DNA in human samples is generally estimated in the 1-5% range in various locations and populations, with some indication of age-dependence.

[7] Another 2009 study found around 70% seroprevalence for adults, with age patterns indicating that infants may inherit maternal antibodies against both WU and KI.

[11] While no clear association with clinical symptoms has been identified, there is weak indication that WU and KI viruses may have pathogenic potential in immunocompromised patients.

[13] In an updated classification system for the polyomavirus family proposed in 2016, WU virus is classified as a member of the genus Betapolyomavirus along with BK, JC, and KI.