Potential bioterrorism agents by category

The United States Centers for Disease Control and Prevention has ranked various pathogens into these categories based on their potential to cause harm.
Category A agents are the highest priority. They can cause high mortality, can be grown easily in large quantities, and are resistant to destruction. They are also well suited to airborne dissemination and can thus infect large numbers of people.
Category B agents are the second highest priority. They are moderately easy to spread but generally cause less morbidity and mortality than Category A agents.
Category C agents include pathogens that could be engineered for mass dissemination and have significant potential morbidity and/or mortality.