Biological warfare (but not research into defense or protection against biological agents) was outlawed by the Biological Weapons Convention in 1972. Biological weapons are biological toxins or infectious agents such as bacteria, viruses, fungi, or parasites intended to kill or incapacitate and have been widely used throughout history [
37],[
58]. With the exception of some rapidly acting toxins, biological agents usually present only hours or days after exposure with non-specific `flu-like’ symptoms before organ-specific diseases become apparent [
58]. The risk presented by biological agents can be classified by their individual pathogenicity, infectivity, latency, lethality, transmissibility, and virulence. The US Centers for Disease Control and Prevention categorize agents depending on the threat that they may pose to national security because of their dissemination, person-to-person transmission, high mortality rates, potential for social disruption, and need for public health preparedness. The Category A (highest priority) organisms are rarely seen in the US and include anthrax, botulism, plague, smallpox, tularemia, and viral hemorrhagic fever [
59]. Category B agents are more commonly encountered and include food-and-water safety threats such as Salmonella species,
Escherichia coli 0157:H7, and
Vibrio cholerae. Ricin is the Category B agent most frequently encountered in the US, can be easily prepared from castor beans, and has been used in `white powder’ letters. Although such acts have been largely criminal in nature rather than true bioterrorism and are frequently hoaxes, such incidents pose a potential threat to emergency medical responders [
60]. Successful terrorist use of biological weapons is extremely rare, and one source suggests that only two confirmed terrorist biological attacks have harmed humans [
61].
Between October and December 2001, widespread fear was caused across the US by a series of letters containing anthrax spores that were sent to government buildings. Five people died from anthrax, 13 contracted disease, and many thousands were exposed and took preventative antibiotics. Health-care personnel were not specifically targeted, although other emergency services required to deal with suspicious packages were exposed to risk [
62].
The difficulty in identifying biological attacks is apparent from the Salmonella typhi outbreak in The Dalles, Oregon, in 1984 when 751 citizens were affected [
63]. Only 1 year later did it emerge that the Rajneeshee cult had intentionally contaminated water and salad bars in an attempt to influence a local election result. Similarly, when the Aum Shinrikyo cult was investigated in the wake of the 1995 Tokyo sarin subway attacks, it was discovered that they had built three laboratories to culture
Bacillus anthracis, botulinum toxin, and
Coxiella burnetti and carried out nine undetected biological weapon attacks between 1990 and 1993 [
58],[
64].
Secondary biological threat has been identified as a consequence of exposure to contaminated biological material in explosive incidents. Following the London bombings of 7 July 2005, bone fragments from other victims were found embedded as biological foreign bodies within the soft tissues of five patients at one receiving hospital [
65]. Similar events have occurred in suicide bombings in Israel and in conflict zones against US military personnel, and protocols have been established for post-exposure interventions to prevent infection with hepatitis B and C, HIV, or tetanus [
66]-[
68].