New evidence suggests that a virus, cytomeglaovirus (CMV), can be detected in several different tumors such as brain tumors, neuroblastoma, breast, colon and prostate cancer. We also find the virus in metastases from these tumors, but not in healthy tissue surrounding the tumor cells, suggesting that CMV plays an important role in the development of these tumors. Recently, we discovered that it is not the usual form of CMV that is found in tumors, but instead a new CMV variant that is detected in 90-100% of said tumors. We believe that the new CMV variant can play a significant role in tumor development, and that therapies targeting this virus in the future will hopefully be able to be used to improve existing cancer treatment as it may be able to target the root cause of the tumor. Our experience today shows that brain tumors treated with anti-CMV drugs have a significantly improved survival two years after diagnosis, indicating that this strategy may be possible in the future. In this project we will characterize the new CMV strain, identify new biomarkers for the virus for clinical diagnostics and we intend to develop new treatment strategies for CMV positive cancers.