For the first time ever, a intravenous injection of a virus has been shown to be able to target and kill cancer cells. The trial used a modified vaccinia virus (JX-5694), a type of virus used to make vaccines. Importantly, the virus was able to move through the body and specifically attack cancer cells without harming normal cells. The test was designed to see if the virus could find the cancer cells (and not test how well it would work) but even a single injection resulted in positive results for some of the patients. In addition to the natural ability of the virus to kill cancer cells, the research showed that the virus might be able to deliver additional toxic genes to the cancer cells.