Growing numbers of people are moving within and across national borders after being forced from their homes by war, poverty, or famine. According to some estimates, 1 billion people could be displaced by 2050. Displaced people often bring their livestock, plants, or companion animals with them, increasing the variety of pathogens and vectors that accompany such journeys. Such refugees frequently live in crowded, unsafe conditions that exacerbate the transmission of infectious diseases. Rural to urban migration, for example, has led to increased HIV transmission in Africa.
Bioterrorism is the deliberate release of viruses, bacteria, toxins, or other agents to cause illness or death in people, animals, or plants. According to experts, the threat of global bioterrorism is increasing. In October 2001, bioterrorism became a reality when letters containing powdered anthrax were sent through the U.S. Postal Service. The attack caused 22 cases of illness, 5 of which resulted in death, and widespread fear.
Biological agents are in some ways the perfect weapon of terror. They can be spread through the air, water, or food. Terrorists may choose these agents because they can be extremely difficult to detect and do not cause illness for several hours to several days after exposure, meaning that public health officials may not notice the attack until it is too late. Deadly pathogens are highly accessible. With the exception of smallpox, they all occur naturally in the wild—in soil, air, water, and animals. And the skills and equipment for making a biological weapon are widely known because they are the same as those required for cutting-edge work in medicine, agriculture, and other fields.
High-priority organisms or toxins that pose the greatest risk to national security are known as Category A agents, according to the National Institute of Allergy and Infectious Diseases (NIAID). These deadly pathogens could be readily spread in the environment or transmitted from person to