BK Virus Infection

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What is BK Virus Infection?

BK virus is a virus that rarely causes disease or severe symptoms. After entering into human body, it disseminates to the kidneys, brain, blood etc. and settles down, without disturbing the hostís health. Symptoms of infection from BK virus surface under conditions when the immunity of the individual reduces. Thus, an increase in number of BK virus infection cases was noticed when newer immunosuppressive drugs like mycophenolate mofetil and tacrolimus came to be used in organ transplant patients to prevent organ rejection.

BK virus was first isolated in 1971 and belongs to the polyomavirus family. The virus was isolated from the urine of a patient who underwent renal transplant and was named BK after him.

BK Virus Infection

The BK virus normally remains inactive in the blood, kidneys, or other organs of the patient. Transmission from one person to another occurs through fluids like respiratory tract fluids, saliva and urine. The infection can also spread from a mother to her baby during birth.

Risk Factors for Severe BK Virus Infection

Severe symptoms of BK virus infection may be present under certain conditions such as:
  • Age: As one gets older, the immunity system of our body weakens giving way to many infections. The BK virus which would have been present in the body can cause problems during this time.
  • Organ transplant: Patients undergoing organ transplant are given potent immunosuppressive agents so that the new organ is not rejected. This can make the BK virus stronger and present with symptoms.
  • Weakening of immune system: Health conditions such as AIDS and diabetes can make the immune system weaker. Under such an environment, the BK virus can grow inside the body, causing symptoms to flare up.

What are the Symptoms and Signs of BK Virus Infection?

BK virus infection usually does not cause symptoms. Sometimes, mild symptoms like fever or body aches may be present as soon as the virus infects the person. However, when the infected personís immunity is suppressed by medicines like following organ transplants, then the following symptoms may be present:
  • Brown or red urine
  • Pain during urination
  • Difficulty in urination or other problems with urination
  • Fever, muscle pain or weakness
  • Difficulty with breathing, cold and cough
  • Vision changes
  • Seizures
  • Urine examination shows the presence of renal tubular cells and inflammatory cells.
Symptoms of severe infection include the following:
  • Nephropathy, or kidney dysfunction or damage
  • Asymptomatic hematuria (Blood in urine)
  • Hemorrhagic cystitis (sudden onset of hematuria with bladder pain), which is often difficult to treat
  • Urethral stenosis (narrowing of urethra Ė the tube that takes urine from bladder to outside the body)
  • Interstitial nephritis (infection of interstitium of kidney)
  • Pneumonitis and pneumonia due to infection of the lungs
  • Rarely, brain, liver and eye disease
The role of BK virus in causing systemic lupus erythematosus and some cancers has also been suggested.

Symptoms of BK Virus Infection

How to Diagnose BK Virus Infection?

The following tests help in confirming the diagnosis of BK virus infection:
  • BKV blood test or urine test
  • Complete urinalysis
  • Presence of decoy cells in urine
  • Biopsy of kidneys
  • Polymerase Chain Reaction techniques
Diagnosis of BK Virus Infection

What are the Treatments for BK Virus Infection?

The main aim of treatment for BK virus infection is reduction in immunosuppression. If the patient is taking drugs like tacrolimus and mycophenolate mofetil, he or she is asked to replace them with cyclosporine.

Leflunomide is an antiviral drug with immunosuppressant properties that is often administered to kidney transplant patients with BK infection.

Drugs like cidofovir, another antiviral drug and fluoroquinolones are also used for the treatment of BK virus.

Treatment for BK Virus Infection

Bladder irrigation is a continuous or intermittent flow of a saline or medicated solution passed through the bladder to wash out unwanted substances from the bladder. This procedure is used to wash out any viral growth in the bladder in case of BK virus infection.

What is the Prognosis of BK Virus Infection?

The presence of BK virus in the body is not usually harmful and the person can remain asymptomatic for life. However, if the patient has to undergo a kidney transplant or bone marrow transplant, the virus tends to grow in the allograft or in the blood as the patient receives immunosuppressive drugs to counteract the rejection of the transplanted organ.

Once the symptoms flare up, the patient can be treated with drugs to suppress the virus. Hemorrhagic cystitis is one of the uncontrollable symptoms of BK virus infection and may also be fatal for the individual. So, it is best to undergo a diagnostic test for the presence of BK virus in blood or urine before the surgery for transplantation.

Health Tips

  • Prevention of BK virus infection involves identifying the disease with BKV diagnostic tests.
  • Before going for an organ transplant it is essential to undergo tests to detect BK virus and its related virus called JC virus.
  • Post-transplantation patients must also be assessed for the presence of virus. Allograft biopsies can help in the detection of the virus.
  • Immunosuppressive therapy must be given with care keeping in mind the possibility of presence of the BK virus in the patientís blood and kidneys.


1. http://cid.oxfordjournals.org/content/33/2/191.full

2. http://en.wikipedia.org/wiki/BK_virus

3. http://cjasn.asnjournals.org/content/3/Supplement_2/S68.full

4. http://www.ncbi.nlm.nih.gov/pubmed/19064383

5. http://cjasn.asnjournals.org/content/2/Supplement_1/S36.full

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