Terrorists could deliberately release biological substances that harm or kill people, animals, and plants. Bacteria, viruses, and toxins—the main types of potential biological “agents”—occur in nature but can be altered to increase their ease of dispersion, potency, or resistance to medicines.
Biological agents can be hard to detect, and their effects may be delayed. A biological attack could come without warning, and the danger may not be immediately recognized. The first alert may be from health-care workers noting an unusual pattern of illness. Your first warning would likely be an emergency broadcast or some other signal used in your community.