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BK virus is a very common , and nine out of 10 people catch it during childhood in the same way as you catch a cold
Rebecca Whittaker,Nicole Wootton-CaneWednesday 03 December 2025 19:21 GMTComments
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When Tim Tavender developed a common virus he had no idea it was the start of what would later become a cancer diagnosis.
The 51-year-old from Southampton became ill with BK virus, also known as polyomavirus, in 2015 following a kidney transplant. Six years later he went to the doctors after noticing blood in his urine, and was handed a devastating diagnosis of bladder cancer - which doctors now say was likely linked to his BK infection.
His story comes as new research shows the virus, which most pick up in childhood and has similar symptoms to the common cold, can trigger DNA damage that can lead to bladder cancer later in life.
Mr Tavender said the new research could be “life changing”.
“It was a terrifying experience,” he continued. “BK virus made me feel sub-par, like constantly having the flu, and lowering my immunosuppressants to fight it left me walking a medical tightrope.
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Simon Baker from the University of York, has researched how the BK virus leads to bladder cancer (Kidney Research UK)“Then, in 2021, I noticed blood in my urine. It wasn’t just a little bit, it was claret. That visit to the doctor probably saved my life.”
The study published in the journal Science Advances, used human tissue that lines the urinary tract and exposed it to the BK virus.
Researchers then looked for changes in DNA and found in the fight against the BK virus, “friendly fire” from enzymes meant to damage the virus can cause collateral damage in the cells’ own DNA.
“We found that DNA damage happens not only in infected cells but also in surrounding ‘bystander cells’, witnessing infection in their neighbours. This is important because it might explain why most bladder cancers have no sign of the virus in them when they are diagnosed many years later,” Dr Baker said.
The virus usually lies dormant in the kidney, but for transplant patients who have taken immunosuppressants to prevent the immune system from targeting the new kidney, it can allow the virus to reactivate and damage the kidneys and bladder.
Mr Tavender had a 13-hour long surgery to remove his bladder and hopes the new research will spare others from going through what he did.
There are around 10,000 new bladder cancer cases in the UK every year. Current advice to prevent bladder cancer includes quitting smoking, but this study provides a new opportunity to help prevent the cancer through identification and control of BK virus earlier.
Dr Baker said: “We can now see how BK virus may contribute to bladder cancer, in transplant recipients and the general population, and explain why tumours show no trace of the virus years later. It gives us motivation to seek prevention strategies for both bladder cancer and the kidney damage caused by BK virus. With support from Kidney Research UK and York Against Cancer, our lab is developing new ways to control BK virus.”
Dr David Crosby, chief research officer at Kidney Research UK, commented: “These findings move us closer to understanding why some people develop bladder cancer and show how tackling BK virus early could one day stop these cancers from developing at all.”
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