The use, or threatened use, of biological agents to promote or spread fear or intimidation upon an individual, a specific group, or the population as a whole for religious, political, ideological, financial, or personal purposes. These biological agents, with the exception of smallpox virus, are typically found in nature in various parts of the world. They can be, however, weaponized to enhance their virulence in humans and make them resistant to vaccines and antibiotics. This usually involves using selective reproduction pressure or recombinant engineering to mutate or modify the genetic composition of the agent. Bioterrorism agents may be disseminated by various methods, including aerosolization, through specific blood-feeding insects, or food and water contamination.