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[Microbiology](https://durgical.com/en/microbiology/) · [Other DNA viruses](https://durgical.com/en/microbiology/groups/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

## Key points

- JC = brain (PML); its relative BK = transplanted kidney and hemorrhagic cystitis.
- PML: AIDS or natalizumab, white-matter lesions and JC PCR in CSF.
- Treatment: restore immunity; there is no effective antiviral.
- It kills oligodendrocytes: a demyelinating disease.

## 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

## Memory aid

JC = Judgment Cleared: in the immunocompromised the virus erases white matter, and judgment and strength go with it.

## 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.

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## Related

- [Cytomegalovirus](https://durgical.com/en/microbiology/cytomegalovirus/)
- [Adenovirus](https://durgical.com/en/microbiology/adenovirus/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Other DNA viruses](https://durgical.com/en/microbiology/groups/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](https://medlineplus.gov/ency/article/000674.htm) (MedlinePlus (NLM), 2024); [Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions](https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html) (CDC, 2024).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/jc-polyomavirus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/jc-polyomavirus/