Disease is among the oldest and most elemental threats to human society. Diseases like plague and smallpox shaped the course of human history, shattered societies, and transformed populations. The flu pandemic of 1918 killed as many as 50 million people worldwide, dwarfing the 17 million death toll of the “Great War” that just preceded it. Disease can strike rich and poor, east and west with impunity—but it preys most cruelly on the weak, the vulnerable, and the poor. Given the power of disease over society, it is no surprise that health care, along with food, water, and shelter, is among the most basic and vital service people require and a fundamental test of the value of governments and institutions entrusted with providing it. Mother Nature can wreak havoc enough, but she is by no means the only threat. The deliberate, malicious use of disease is among the gravest and most horrifying of national security threats—against which our defenses are limited at best. The 2001 anthrax attacks only resulted in five deaths but gripped the nation in fear, brought the postal system to a near standstill, and cost the nation more than $1 billion in response and recovery. Fourteen years hence, it is still prudent and chilling to weigh the implications of a larger more effective attack or one involving a contagious pathogen. Read the full commentary here.