What is BK Virus?
Infectious Diseases Data Verified

BK Virus - Symptoms, Diagnosis, and Treatment

Published on Jun 01, 2023 and last reviewed on Jul 17, 2023   -  5 min read


BK virus is a type of common virus that is widespread but does not cause excessive symptoms upon infection. Read on to learn more about this virus.


Viruses are very tiny germs. They are composed of genetic material within a protein shell. Viruses cause known infections such as colds, flu, and warts. Viruses are like tiny hijackers of the body. They invade normal living cells and use those cells to replicate and produce other viruses like themselves. This can kill, damage, or alter cells, making them sick. Various viruses attack specific cells in the body, like the liver, respiratory system, or blood. Being infected with a virus does not necessarily mean that a person will get sick. Their immune system may be able to fight it off without any signs or symptoms. BK polyomavirus (BKV) causes frequent infections in childhood and persistent infections of kidney cells but has a minimal clinical impact.

What Is BK Virus?

The BK virus belongs to the Polyomavirus family and is named after the kidney transplant patient in which it was first identified. The BK virus is a virus that most people are infected with during childhood. Symptoms may feel like a cold. Once infected with the BK virus, the virus remains in your system forever. But for most people, it shouldn't be a problem. It's like lurking in the body or sleeping. Viruses can wake up when the immune system does not work well. Later, symptoms of infection may appear. BK virus is also known as polyomavirus.

What Are the Causes of BK Virus Infection?

The causes of BK virus infections are listed below:

  • Organ transplant.

  • Kidney surgery or injury.

  • Older age.

  • Health conditions that weaken the immune systems like HIV and diabetes.

  • From others (by coughing, sneezing, or close contact).

  • From surfaces or objects (counters, doorknobs, phones, etc.) touched by an infected person.

What Are the Risk Factors of BK Virus Infection?

Symptomatic flare-ups due to infection or reactivation of the BK virus can occur when a person's immunity is weakened by:

  • Those over the age of 60.

  • Use of potent immunosuppressants in organ transplantation.

  • HIV infection and diabetes.

  • Kidney transplant recipients.

  • Those on Prednisone corticosteroid.

  • Organ recipients who are diabetic appear to be at greater risk for the development of BK virus.

What Are the Symptoms of BK Virus Infection?

A doctor will check your system for signs of the virus. The BK virus can wake up, so it's important to watch for signs of infection. The symptoms include:

  • Vision changes, such as blurred vision.

  • Urine color change (brown or red urine).

  • Pain when urinating.

  • Difficulty urinating.

  • Increased urination.

  • Cough, cold, or difficulty breathing.

  • Fever, muscle pain, or weakness.

  • Seizure.

  • Brown or red urine with small amounts of hematuria.

  • Fever, muscle pain, or weakness.

  • Difficulty breathing, cold, cough.

  • Deterioration of kidney function due to kidney inflammation (interstitial nephritis).

  • Scarring narrows the tube that carries urine out of the bladder (urethra).

  • Pneumonia and pneumonia due to lung infection.

  • Changes in the vision.

  • Seizure.

  • Brain, liver, or eye disease.

How Is BK Virus Infection Diagnosed?

The following tests can help confirm a diagnosis of BK virus infection.

  • BKV Blood Or Urine Test - To detect the presence of the BK virus antigens in the blood and urine samples taken in the lab. A pathologist will conduct this test on the microscope.

  • Urine Microscopic Examination - To look for abnormalities, such as the presence of decoy cells in the urine.

  • Renal Biopsy - To detect damage to the kidneys. The small section of the kidney is removed and checked under the microscope for any abnormalities.

What Is the Treatment of BK Virus Infection?

The ways to treat BK virus infection are listed below:

  • The primary treatment for BK virus infection is to adjust immunosuppressive agents such as Tacrolimus, Mycophenolate Mofetil, and steroids to reduce immunosuppression.

  • Leflunomide is an antiviral drug with immunosuppressive properties and is commonly administered to renal transplant patients with BK virus infection.

  • Drugs such as Cidofovir, other antiviral drugs, and Fluoroquinolones are also used to treat the BK virus.

  • Irrigation of the bladder is the continuous or intermittent flow of saline or medicated fluids through the bladder to flush unwanted substances from the bladder. This procedure may be used to flush out viral growth buildup in the bladder in case of BK virus infection.

What Is the Outcome of BK Virus Infection?

In otherwise healthy people, the presence of the BK virus in the body is usually harmless and can remain asymptomatic for life. However, if the patient has a bone marrow or kidney transplant, the virus grows in the allograft or blood as the patient is administered immunosuppressants to prevent rejection. Reducing immunosuppressants may suppress viral load. Hemorrhagic cystitis (inflammation of the bladder) can be a difficult problem with a BK virus infection. Before a transplant surgery, a diagnostic test for the presence of the BK virus in urine and blood may be recommended.

How to Prevent BK Virus Infection?

The prevention of the BK Virus is done in the ways listed below:

  • Prevention of BK virus infection includes identification of the disease with a BKV diagnostic test.

  • An individual may need to be tested to detect the BK virus before organ transplantation.

  • After transplantation, the presence of the virus should be rechecked. Allograft biopsy can help detect the BK virus.

  • Immunosuppressive therapy should be used with caution, given the potential presence of the BK virus in the patient's blood and kidneys.


BK virus is transmitted from one person to another through respiratory secretions, saliva, urine, and during childbirth. After the initial infection, it lurks in the patient's blood, kidneys, or other organs. Human-to-human transmission occurs through bodily fluids such as respiratory fluids, saliva, and urine. It can also be passed down from mother to baby during childbirth. A suppressed immune system is so weakened that it is unable to mount an adequate immune response to protect the body from pathogens such as bacteria, viruses, and other infectious organisms. As a result, people with weakened immune systems are more susceptible to various infections. BL virus infection is one such illness that can take over the body in its immunosuppression stage. Antiviral medications are given for the treatment of this illness. This illness is mainly found in patients receiving kidney transplants.

Article Resources

Last reviewed at:
17 Jul 2023  -  5 min read




Comprehensive Medical Second Opinion.Submit your Case

Popular Articles Most Popular Articles

Do you have a question on Bk Virus or ?

Ask a Doctor Online

* guaranteed answer within 4 hours.

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.