The common cold virus could cure cancer, scientists say, as a "revolutionary" treatment is predicted 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 forms of the disease.
They said the virus could become a "universal agent" to fight cancer, replacing treatments such as 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 patients, researchers said. They hope the treatment could be available in as little as three years.
About 500 people in Ireland are diagnosed with bladder cancer annually.
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 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 cancers.
Prof 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 use of the virus could "revolutionise" treatment.
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 well-being by destroying cancerous cells." (© Daily Telegraph, London)