Researchers at the University of Ottawa have designed a virus that selectively targets cancer cells located anywhere in the body. Based on the vaccinia virus, which was used to develop a smallpox vaccine, the virus depends on a chemical pathway to replicate itself. The virus is injected into a vein and circulates throughout the body via the bloodstream. A total of 23 cancer patients were injected with varying amounts of the virus. Seven out of eight patients who received the highest dose were found to have the virus replicating in their tumors as expected. The infection prevented tumor growth in six of those patients. Researchers were particularly encouraged that the virus impacted mesothelioma tumors that are very difficult to treat by traditional methods.