An engineered virus, injected into the blood, can selectively target cancer cells throughout the body, according media reports Thursday quoting a study in journal Nature. The virus attacked only tumors, leaving the healthy tissue alone, in a small trial on 23 patients. \"We are very excited because this is the first time in medical history that a viral therapy has been shown to consistently and selectively replicate in cancer tissue after intravenous infusion in humans,” said John Bell, a lead researcher and from the University of Ottawa. It is believed that the virus could be used to deliver treatments directly to cancerous cells in high concentrations. Using viruses to attack cancers is not a new concept, but in this study they have been injected directly into tumors in order to evade the immune system. Bell acknowledged that the research is still in the very early stages, but he said: \"I believe that some day, viruses and other biological therapies could truly transform our approach for treating cancer.\"