The common cold virus could cure cancer, scientists say, as a “revolutionary” treatment was found to eradicate the disease in a week.
In the pioneering British trial, 15 patients were given an infusion of the bug, before undergoing surgery to remove and examine tumours.
In every case, cancer cells had been destroyed - and in one case, all traces of the disease had gone, the study found.
Scientists said they were “very excited” about the findings, for patients with bladder cancer, which could also bring hope to those suffering from other major forms of the disease.
They said the virus could become a “universal agent” to fight cancer, replacing conventional treatments like chemotherapy.
As well as reducing the size of all the tumours, the treatment, via a catheter to the bladder, had no significant side-effects in any of the patients, researchers said.
Bladder cancer is the tenth most common type of cancer in the UK, with 10,000 diagnoses annually.
Scientists said they hoped the treatment could be available in as little as three years, bringing hope to thousands of patients with diseases that are currently hard-to-treat.
Most tumours in the bladder do not have immune cells, making the disease particularly hard to treat.
But the study suggests that an infusion of a strain of the common cold virus - called coxsackievirus (CVA21) - was able to inflame the tumour and cause immune cells to rush into the cancer environment, targeting and killing the cancer cells.
Scientists said once the virus targeted the cancer, it replicated itself, making its effects even more powerful.
Prof Hardev Pandha, Principal Investigator of the study and Professor of Medical Oncology at the University of Surrey, said: “We are very excited about it. The virus gets into the cancer and replicates, like a little factory of viruses. It heats up the tumour environment, and is very specific in targeting the cancer - it had the least toxicity I have seen for years.”
It comes as other trials examine the role of common cold viruses to treat a range of cancers, including breast, bowel, lung and skin diseases.
Prov Pandha said: “It’s almost like a universal agent - once it gets in it kills the cancer. It could be combined with lots of other treatments.”
He said the use of the virus could help “revolutionise” treatment for the disease.
The study, with Royal Surrey County Hospital, involved patients non-muscle invasive bladder cancer, which is found in the tissue of the inner surface of the bladder.
When tissue samples were examined after surgery, scientists could see that only the cancerous cells had been targeted - with other cells left intact.
The virus was found to have infected cancerous cells and replicated itself causing the cells to rupture and die.
And urine samples taken from patients after the treatment detected “shedding” from the virus - indicating that once virally infected cancer cells had died, the newly replicated virus continued to attack more cancerous cells.
“Reduction of tumour burden and increased cancer cell death was observed in all patients and removed all trace of the disease in one patient following just one week of treatment, showing its potential effectiveness. Notably, no significant side effects were observed in any patient,” the research found.
Scientists said the success of the trials was particularly significant because current treatments for the disease have limited success.
Transurethral resection, an invasive procedure that removes all visible lesions, has a high chance of disease recurrence, with rates ranging from 50 per cent to 70 per cent.
Dr Nicola Annels, Research Fellow at the University of Surrey, said: "Traditionally viruses have been associated with illness - however in the right situation they can improve our overall health and wellbeing by destroying cancerous cells.”
She said the use of the viruses “could transform the way we treat cancer and could signal a move away from more established treatments such as chemotherapy."
Dr Mark Linch, from Cancer Research UK, said: “Although at an early stage, these initial results are encouraging. It will be really interesting to see how this new virus-based therapy fares in larger trials in people with non-muscle invasive bladder cancer, particularly in combination with newer immunotherapies.”