Historical Perspective on Biological Attack
- In 2001, anthrax attacks through the U.S. mail infected 11 people with inhalational anthrax, of which five died. An additional 11 people were infected with cutaneous (skin) anthrax, of which there were no fatalities.
- In the 1990s, the cult Aum Shinrikyo failed in its attempts to release anthrax and botulinum toxin in Tokyo but did succeed in a chemical attack with Sarin nerve agent.
- In 1984, the cult followers of Baghwan Shree Rajneesh sickened 751 people in Oregon by placing salmonella bacteria in salad bars in 10 restaurants to keep people from voting in an election.
- In World War II, Unit 731 in Japanese-occupied Manchuria dropped plague-infected fleas in China, allegedly resulting in more than 50,000 deaths.
- In World War I, German agents successfully infected Allied livestock with anthrax and glanders.
- In the 1340s, Europeans threw plague-infected cadavers over city walls to infect those within.
Impact on Human Health
Biothreat agents have the potiential to produce a life-threatening illness. Biotoxins are essentially poisons that can be fatal at high enough doses. Table 1 lists health impacts and medical treatments for the Category A and some Category B agents. Even a small amount of some biothreat agents released in air could result in significant loss of life, depending on a number of factors including:
- Infectivity of the agent (how many particles are needed to cause illness).
- Lethality of the agent.
- Length of time it takes to detect and treat those who are exposed or have become ill.
Dose Response in Humans
The exact infectious dose (the number or organisms needed to make one sick) of most biological agents is unknown; approximate doses are extrapolated from animal studies. Whether a person becomes ill after exposure to a biological agent depends on a number of factors including:
- Type and amount of agent taken into the body.
- Duration of exposure.
- Route of exposure (inhalation, ingestion, insect bite).
- "Host" factors (e.g., age, immune status, other illnesses of the person exposed).
Differences in Intentional vs. Natural Outbreaks of Disease
Naturally occurring outbreaks of category A agents have become rare because of improved living standards, hygiene, and health services in developed nations. For example, human bubonic plague,which was transmitted by rats and fleas to humans in past centuries resulting in large losses of life, has virtually been wiped out. However, agents used in an aerosol attack may act differently than naturally occurring outbreaks and could produce a form of the disease with a shorter time of onset of illness, making timely diagnosis, treatment, and containment more difficult.
Spread of Diseases
Some transmissible (contagious) diseases can spread through respiratory droplets from coughing and sneezing or when a person comes in contact with a surface harboring a virus or bacteria and then touches their mouth or nose. The viral hemorrhagic fevers and cholera are spread by direct contact with body fluids or feces. People infected with contagious diseases may widely disseminate the disease by travel.
Psychological responses following a bioterrorism event may include anger, fear, and social isolation. Following the 2001 anthrax attacks, thousands of people who thought they were infected sought treatment. Trying to distinguish those who haven't been infected could complicate medical centers' ability to treat those who have been exposed and infected, especially when diagnoses are unclear.