A virus is specific to a person. They hope they can get a virus bioengineered against the laws of nature such that it can be effectively released to either selectively kill an individual or a specific spectrum of genetically similar individuals. It makes it a lot easier when people willingly let them stick things up their noses, or even better, inject into their bodies.

The clone angle probably has a lot of possibility, too. When you're financing over 100 illegal biolabs, they can't all be working on viruses.