This isn’t true. Viruses are subject to evolutionary pressure even inside a single patient. They don’t replicate perfectly (partly because they have to be small and simple, and don’t have very good control of the cellular environment they are inside, being invaders and all) and so variants of the particle compete with one another. Because of this, features that might be desired in a bioweapon but are not needed in order for the virus to replicate can get lost.
For instance, a bioweapon virus might contain genes for botulism toxin in order to kill the host. However, copying this gene every generation would diminish the particles ability to replicate, and so variants of the particle that are missing the gene would have a small evolutionary advantage. After just a few patients, the wild version of the virus might have lost this feature.
This isn’t true. Viruses are subject to evolutionary pressure even inside a single patient. They don’t replicate perfectly (partly because they have to be small and simple, and don’t have very good control of the cellular environment they are inside, being invaders and all) and so variants of the particle compete with one another. Because of this, features that might be desired in a bioweapon but are not needed in order for the virus to replicate can get lost.
For instance, a bioweapon virus might contain genes for botulism toxin in order to kill the host. However, copying this gene every generation would diminish the particles ability to replicate, and so variants of the particle that are missing the gene would have a small evolutionary advantage. After just a few patients, the wild version of the virus might have lost this feature.