An engineered virus, injected into the blood, can selectively target cancer cells throughout the body in what researchers have labelled a medical first. The virus attacked only tumours, leaving the healthy tissue alone, in a small trial on 23 patients, according to the journal Nature. Researchers said the findings could one day truly transform" therapies. Cancer specialists said using viruses showed "real promise". Using viruses to attack cancers is not a new concept, but they have needed to be injected directly into tumours in order to evade the immune system. The virus, named JX-594 ... was injected at different doses into the blood of 23 patients with cancers which had spread to multiple organs in the body. Prof John Bell, lead researcher and from the University of Ottawa, said: "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. Intravenous delivery is crucial for cancer treatment because it allows us to target tumours throughout the body as opposed to just those that we can directly inject."