National Institutes of Health (NIH) and United States Public Health Service (USPHS) Stewart joined the
National Institutes of Health (NIH) as a bacteriologist from 1935 to 1944 while completing her PhD at the University of Chicago. Stewart retired from the United States Public Health Service in 1970 and became a professor in the Department of Pathology at Georgetown University until 1974. In addition, the two fields of cancer research and viruses were thought to be completely separate, as their connection was commonly disregarded by the scientific community at the time. This led to the common belief that virologists were not qualified to take part in cancer research, whereas microbiologists were thought to be overqualified. Building on earlier work by
Ludwig Gross, Stewart and Bernice E. Eddy were the first to describe a polyomavirus. They did so by injecting the mice with ground organs of other mice that were known to contain leukemia, and observing cancerous tumor growth that was unrelated to leukemia. Although it has been demonstrated that SE polyoma virus produces tumors in rodents under laboratory conditions, it is known that the
parotid gland tumors and others of the spectrum produced in mice rarely are found under natural conditions, even though it has been found that many mouse colonies have the virus as a latent infection. Stewart and Eddy continued to test the theory that viral components are able to induce tumors. They tested tumor extracts from both monkey and mouse embryos, and found that the mouse embryos contained a higher quantity of cancer causing viral agents. This lead them to reason that viruses can be causative agents of cancer. Some of the tumors observed were angiomatous sarcomas in Syrian hamsters, sarcomas in rats, and mesenchymal nodules in rabbits. Eddy and Stewart demonstrated that the virus causes cell necrosis and proliferation in cell culture, that it is highly antigenic, and that it leads to formation of specific antibodies in infected animals whether or not tumors develop. At Eddy's suggestion, the virus was dubbed "polyoma", meaning many tumors. The virus was named the Stewart–Eddy or SE polyoma virus, after their respective surnames. It became known that there were some viruses that could lead to or be a cause for certain cancers. Stewart developed an interest in researching these viral links to cancer in light of the pioneering research of
Jonas Salk in developing a vaccine for the virus which caused
polio. ==Death and afterward==