Microbiology · Other DNA viruses
JC polyomavirus !
- Virus
- Non-enveloped (naked)
- Exam priority: medium
A virus most people carry without symptoms; in the immunocompromised it destroys brain myelin (PML).
Updated 2026-11-01
Also called: JC virus, JCV
At a glance
- Shape
- Icosahedral, non-enveloped
- Genome
- Circular double-stranded DNA
- Envelope
- Non-enveloped (naked)
- Family
- Polyomaviridae
- Size
- About 45 nm
Morphology
- Naked icosahedral capsid
- In the brain it infects oligodendrocytes, the cells that make myelin
Transmission
- Probably respiratory or oral in childhood; most people are infected before age 10
- The disease is not caught: it is reactivation of the person's own virus
Reservoir: Humans (latent in kidney and bone marrow)
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- Latency in kidney and lymphoid tissue
- Reactivation when cell-mediated immunity fails
- Lysis of oligodendrocytes with multifocal demyelination of white matter
Diseases it causes
- Progressive multifocal leukoencephalopathy (PML)
Clinical picture
- Progressive weakness, clumsiness, speech and vision problems, cognitive change
- Patients with advanced AIDS, blood cancers or immunosuppressive monoclonal antibodies (for example natalizumab in multiple sclerosis)
- A severe disease: a large share of patients die within the first year
Diagnosis
- MRI: multifocal white-matter lesions without mass effect
- JC virus PCR in cerebrospinal fluid
- Brain biopsy in unclear cases
Treatment
No antiviral works. The backbone is restoring immunity: antiretroviral therapy in HIV and stopping the responsible immunosuppressant; immune reconstitution inflammatory syndrome may follow.
Drug class only; doses and regimens are set by the clinician from the current guideline.
Prevention
- HIV control
- PML risk monitoring in patients on immunosuppressive monoclonal antibodies
- Standard precautions
Test yourself
Think of the answer, then tap the question to see it.
Which cell does JC virus destroy in PML?
The oligodendrocyte, causing multifocal demyelination of white matter.
Which multiple sclerosis drug is classically linked to PML?
Natalizumab, a monoclonal antibody that blocks lymphocyte entry into the central nervous system.
What is the backbone of PML treatment in a person with HIV?
Starting or optimizing antiretroviral therapy to restore immunity, since no antiviral works against JC virus.
Related
← Back to the group: Other DNA viruses
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Progressive multifocal leukoencephalopathy (MedlinePlus (NLM), 2024); Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions (CDC, 2024).
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Representative model, for educational purposes only.