Bioweapons are normally not meant to be transmitted human to human on a large scale. It is a popular view that something like Sars viruses would be a good agent

Bioweapons are normally not meant to be transmitted human to human on a large scale. It is a popular view that something like Sars viruses would be a good agent, but actually it's not. First: You don't want to infect your own people, especially if your health system is inferior. Containment is impractical. Second: You need to find an agent that satisfies two requirements. It must be able to transmit readily between humans. And it must not have done so already, because that would make most of the potential victims immune. That's basically impossible to achieve.