SUMMARY
Viruses usually infect a restricted set of host species, and only in rare cases does productive infection occur outside the natural host range. Infection of a new host species can manifest as a distinct disease. In this respect, the use of nonβhuman viruses in clinical therapy may be a cause for concern. It could provide the opportunity for the viruses to adapt to the new host and be transferred to the recipient's relatives or medical caretakers, or even to the normal host species. Such environmental impact is evidently undesirable. To forecast future clinical use of nonβhuman viruses, a literature study was performed to identify the viruses that are being considered for application as therapeutic agents for use in humans. Twentyβseven nonβhuman virus species were identified that are in (pre)clinical development, mainly as oncolytic agents. For risk management, it is essential that the potential environmental consequences are assessed before initiating clinical use, even if the virus is not formally classified as a genetically modified organism. To aid such assessment, each of these viruses was classified in one of five relative environmental risk categories, ranging from βNegligibleβ to βVery Highβ. Canary pox virus and the Autographa californica baculovirus were assigned a βNegligibleβ classification, and Seneca Valley virus, murine leukemia virus, and Maraba virus to the βHighβ category. A complicating factor in the classification is the scarcity of publicly available information on key aspects of virus biology in some species. In such cases the relative environmental risk score was increased as a precaution. Copyright Β© 2011 John Wiley & Sons, Ltd.