Which of the following is a Category A agent?

• A. Smallpox
• B. Glanders
• C. Ricin
• D. Tuberculosis

Answer: (A)

Category A agents are the highest-priority threats because they can spread easily, cause severe illness or death in large populations, and trigger widespread panic, demanding rapid, nationwide public health and security responses. Smallpox fits this level because it spreads readily through respiratory droplets and close contact, and historically caused high mortality. Even though vaccination has reduced risk, immunity in the general population is not universal today, so a deliberate release could lead to rapid, large-scale outbreaks without swift containment and vaccination efforts.

Glanders is primarily a zoonotic disease with limited human-to-human transmission, so it does not pose the same immediate, large-scale threat. Ricin is a potent toxin and dangerous, but as a toxin-based threat it is categorized differently from contagious pathogens. Tuberculosis is a serious infectious disease, but it spreads more slowly and there are established treatment options and longer timelines, so it is not classified with the top Category A agents.