"The idea of using pathogens to eliminate neoplastic cells is not a new one. It began in the early 20th century with a report of remission of leukemia in a woman who had acquired a respiratory infection (likely influenza).  In the 1950s and 1960s, interest in oncolytic viruses reemerged, leading to some promising human clinical trials including the use of adenovirus to treat cervical carcinoma. However, during this time period, the ethics of how patients were recruited into clinical trials were highly questionable and oncolytic virus studies were stopped. Since then, ethical guidelines for human clinical trials have been established and there have been critical scientific advances in molecular biology, cancer biology, immunology, and pathogenesis of infectious diseases. These developments have enabled scientists to design recombinant viruses that are no longer pathogenic, but demonstrate improved targeting of neoplastic cells, enhanced oncolytic properties, and/or desirable immunologic effects. In 2005, People’s Republic of China approved a conditionally replicating adenovirus for the treatment of human head and neck squamous cell carcinoma. This oncolytic viral therapy may be beneficial, but its efficacy likely can be improved and additional types of cancers can be targeted."