How Is JC Virus Transmitted From Person to Person?

JC virus is a common infection, often acquired in childhood. Though typically harmless in healthy individuals, it can cause severe complications in those with weakened immune systems. Understanding its transmission is essential for public health and at-risk populations.

This article explores how the virus spreads through direct contact and environmental exposure.

Viral Biology

JC virus (JCV), a member of the Polyomaviridae family, is a small, non-enveloped DNA virus with a circular, double-stranded genome. Its genetic structure is compact, encoding proteins essential for viral replication and host cell manipulation. Structural proteins form the viral capsid, enabling the virus to persist in the human body without immediate disease.

The virus targets human cells expressing specific receptors, such as sialic acid-containing glycoproteins and serotonin receptors, which facilitate entry. Once inside, JCV follows either a lytic or latent infection cycle. In permissive cells, such as glial cells in the central nervous system, it actively replicates, leading to cell lysis and potential neurological damage. In non-permissive cells, like kidney epithelial cells, it remains dormant for years, evading immune detection.

JCV is highly species-specific, with humans as its only known natural reservoir. Unlike other polyomaviruses, it does not cross species barriers, limiting its variability. Genetic studies have identified multiple viral subtypes linked to human migration patterns, indicating that JCV has co-evolved with humans over thousands of years.

Person To Person Contact

JC virus transmission is not fully understood, but evidence suggests close human interactions facilitate its spread. Studies indicate most people acquire the virus in early childhood, with adult seroprevalence rates reaching 50–80% worldwide (Egli et al., Clinical Microbiology Reviews, 2020).

Saliva is a likely transmission route, as viral DNA has been detected in oral secretions. Activities such as sharing utensils, drinking from the same container, or kissing may contribute to its spread (Tan et al., Journal of Virology, 2009). Children, who frequently engage in behaviors that facilitate salivary exchange, are commonly exposed early. However, isolating live virus from saliva has proven difficult, leaving its efficiency as a transmission route uncertain.

Urine is another significant source of viral shedding. JCV establishes a persistent presence in the kidneys, leading to intermittent viral excretion (Kean et al., Journal of Clinical Microbiology, 2009). This suggests potential transmission through contaminated hands, surfaces, or shared sanitary facilities, particularly in households or daycare centers where hygiene practices vary.

Blood-borne transmission is considered rare, though JC virus DNA has been detected in peripheral blood mononuclear cells, raising concerns about its spread via transfusions or organ transplantation (Greaves et al., The Lancet Microbe, 2021). No confirmed cases of transfusion-mediated infection have been documented, suggesting inefficiency in this route. Similarly, while vertical transmission during pregnancy has been investigated, no conclusive evidence supports in utero infection. Instead, postnatal exposure through maternal contact appears more likely.

Environmental Presence

JC virus has been detected in various environmental reservoirs, raising questions about its persistence outside the human body. Wastewater studies consistently identify JC virus DNA in sewage, indicating that viral particles shed through urine and feces enter public water sources. Research suggests JC virus remains stable in aquatic environments, with DNA persisting for weeks in untreated water (Bofill-Mas et al., Applied and Environmental Microbiology, 2006). While this indicates possible environmental dissemination, its role in human infection remains uncertain.

Surface contamination is another potential exposure route. JC virus DNA has been detected on public restroom surfaces, hospital equipment, and communal areas such as daycare centers and long-term care facilities. Its resistance to environmental degradation allows it to persist outside a host, though its ability to remain infectious is unclear. Unlike enteric viruses that cause outbreaks through surface contact, JC virus does not appear to spread widely this way.

Airborne transmission has been explored due to JC virus sequences detected in urban air samples, particularly in areas with high human activity. Although not classified as an airborne pathogen, aerosolized particles from wastewater treatment plants or dust containing viral DNA could contribute to environmental circulation. However, the conditions necessary for viral stability and inhalation-based transmission remain unclear.