Biological agents are microorganisms, such as bacteria, viruses, fungi, or toxins, that can cause disease in humans, animals, or plants. These agents can be naturally occurring or intentionally produced for use in biological warfare or bioterrorism. Examples include anthrax, smallpox, and botulinum toxin. Biological agents can be transmitted through various means, including air, water, or direct contact. They pose significant risks to public health and safety, leading to outbreaks and epidemics. Understanding and monitoring these agents is crucial for preventing and controlling potential biological threats.