BK Virus – Infection, Transmission & Diseases


The BK virus is a polyoma virus. These describe a group of naked virus particles with a DNA genome. The virus occurs all over the world and almost everyone has been infected with the virus, as it is usually transmitted in childhood and persists for a lifetime. The virus is what causes polyomavirus nephropathy , or PVN for short.

What is the BK virus?

The BK virus ( HPyV-1 for short ) is a virus that occurs all over the world. It belongs to the family Polyomaviridae , as well as to the genus Polyomavirus. Human polyomavirus 1 is a synonym for BK virus. The pathogen is probably transmitted in childhood and then subsequently reaches the kidney or the central nervous system (CNS), where it eventually persists throughout life.

During its persistence, the virus can multiply. But this only happens if the humanBodysuffers from a weakness in the immune system , as is the case with AIDS or pregnancy , for example . Therefore, the BK virus is also referred to as an opportunistic pathogen.

The BK virus is a naked virus particle, meaning it is not surrounded by a lipid envelope. That is why the pathogen is much more stable and resistant to various environmental influences than viruses surrounded by a lipid envelope. The genome that carries the virus is double-stranded DNA.

The pathogen was first found in 1971 in the urine of a patient undergoing a kidney transplant. His initials were BK, which is why the virus was named after him.

Occurrence, Distribution & Properties

The BK virus is found all over the world. Around 75 percent of the world’s population carry the virus. Apparently, the pathogen is transmitted in childhood via smear infection with urine, droplet infection or contaminated drinking water and remains persistent in humans for life. When the body becomes infected, the virus spreads to the kidneys or central nervous system.

In the case of an initial infection, infection with the virus occurs in healthy people without any symptoms. However, if the human immune system is weakened, the pathogen can be reactivated and multiply. Virus multiplication is also frequently observed during therapy with immunosuppressants after kidney transplantation . BK nephropathy occurs in about 5 percent of kidney transplant recipients, approximately 8 to 13 months after the transplant. When multiplying, there is also an increased risk of infection, since the pathogen is then increasingly excreted with the urine.

The BK virus does not have a lipid envelope, making the virus more resistant to various environmental influences. For example, disinfection alone is not enough to prevent infection with the virus. This requires special disinfectants .

The BK virus has double-stranded DNA. Only a few viruses are non-enveloped DNA viruses. They also include the adenoviruses , the human papillomavirus , and the second polyomavirus relevant to human medicine, the JC virus .

DNA can be divided into two sections. One section contains the non-coding part that regulates the control region, replication and synthesis of the virus particles. The other section contains the coding part of the DNA. This includes the viral proteins , such as the viral capsid proteins VP1, VP2, VP3 and a so-called agnoprotein. The viral genome is surrounded by an icosahedral capsid. This is a protein coat that forms the virus form and protects the virus. The capsid is made up of the so-called capsomeres, which in turn are made up of the capsid proteins VP1, VP2 or VP3.

Diseases & Ailments

The BK virus is primarily responsible for the so-called polyomavirus nephropathy. This is a kidney disease that frequently occurs after kidney transplants. The virus is present in almost everyone with a prevalence rate of almost 75 percent. It persists in the epithelial cells of the kidney and multiplies when the immune system is weakened.This impairment is primarily caused by therapeutic immunosuppression using tacrolimus or mycophenolic acid , which are typically used for treatment after kidney transplantation. The epithelial cells are damaged and lost. The pathogen is increasingly excreted in the urine, which can infect other people with the virus.

There is also an inflammatory reaction that can be associated with reduced organ function. Polyoma-associated nephropathy (PVN) thus manifests itself as tubulointerstitial nephritis, i.e. as an inflammation of the kidneys. At the beginning of PVN, which occurs in 5 percent of patients after a kidney transplant, there are initially no symptoms. If the blood is examined, however, increased levels of creatinine can occur, which indicate a deterioration in kidney function. In some cases, the ureter narrows , resulting in urinary retention .

Although rare, inflammation of the urinary bladder can still occur. Other non-specific symptoms are fever , skin rash and joint pain , as well as flank pain . In the worst case, transplant rejection occurs .

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.