http://www.mercola.com/2003/jun/21/polio_cancer.htm Many studies have reported the presence of simian virus 40 (SV40) or protein in human brain tumors and bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma, however many of the studies were small or lacking control groups, which made it difficult to determine whether they were reliable. Further, the history of some SV40 infections in humans is linked to the use of polio vaccines. According to conservative estimates, from 1955 to 1963 more than 98 million children and adults in the United States were exposed inadvertently to live SV40 because of SV40-contaminated polio vaccines. The vaccines were also distributed to many other countries and different adenovirus vaccines used on some U.S. military personnel from 1961 to 1965 also contained live SV40. SV40 has been shown to be a potent oncogenic deoxyribonucleic acid (DNA) virus and in animal models, the neoplasias induced by SV40 included primary brain cancers, malignant mesotheliomas, bone tumors, and systemic lymphomas. The current prevalence of polyomavirus SV40 infections in humans is not known because there is a lack of data about which people received contaminated vaccines and the amount of infectious SV40 in particular lots of vaccine. It is also difficult to follow large groups for years after virus exposure for the development of cancer. Analysis of molecular biology data shows that polyomavirus SV40 is associated significantly with primary brain and bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. Further, SV40 may play a role in the development of the malignancies. According to one report, there is moderate strength evidence that SV40 exposure could lead to cancer in humans under natural conditions. Future studies are needed to determine how SV40 is transmitted and how it interacts with different tissues. The American Journal of Medicine June 1, 2003;114(8):675-684