Lethal, non-contagious, vaccine-resistant viruses

More on viruses, this time the biological kind. The New Scientist reports on research into deadly variants on viruses created through genetic engineering. Basically, the virus is enhanced through the addition of a gene (the IL-4 gene) that is responsible for the production of an immuno-suppressant protein. This modification renders the virus immune to traditional vaccines and gives it a lethality rate of 100%. Also, interestingly (and mysteriously), the virus is rendered non-contagious - this means that only directly-infected individuals will succumb: so it would be possible to infect a population and reliably kill all members of the infected population without running the risk of having the disease spread outside this population. All in all, this sounds like a deadly bioterror tool in the making.