Select Agents (SAs) are listed dangerous bacteria, viruses, toxins, and fungi. However, natural variation and intentional genetic modification blur the boundaries of a Select Agent list based on names. Access to new DNA synthesis technologies is making it easier for researchers, industry scientists, and amateurs to create pathogens without access to existing stocks or cultures. This has led to concerns that DNA synthesis might be used to create SAs, introduce small changes to their genetic sequences, or create entirely new pathogens.