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evacuations, as well as in the transport of first responders and to hibernation. When spores settle in favorable condi-
provision of emergency response supplies. Any transportation tions, they become vegetative bacteria, which can grow
modes with large buildings may be considered for use as tem- and reproduce.
porary shelters. Most bacterial diseases can be effectively treated
with antibiotics (i.e., drugs that kill bacteria) if treat-
ment is begun before the onset of symptoms, generally
2.2 BIOLOGICAL THREATS 1 to 4 days after exposure. For anthrax, more treatments
may include vaccination and antitoxins, the latter of
Familiarity with the fundamentals of biological agents can which counteract the toxin that this bacteria produces
be useful in developing appropriate emergency response while growing in the body.
plans. Depending on the particular biological agent, effects · Viruses are much smaller than bacteria. Viruses must be
range from sickness to death, and treatment of infections inside a host cell to replicate, thus they cannot replicate
range from administration of vaccines and antibiotics that before infecting an organism. Two frequently used pro-
may prevent or destroy the infection to simple supportive duction methods for viral replication are cell culture and
care to keep infected people as comfortable as possible while inoculation of fertilized chicken eggs.
their bodies fight the infection. This section addresses bio- Medical treatment of viruses is more difficult than for
logical organisms that may pose either a human health threat bacteria. Diseases from some viral agents (i.e., smallpox
or an agroterrorism threat and toxins produced by biological and certain influenza strains) can be prevented with vac-
organisms. Subsections are fundamentals (2.2.1), emergency cines. Vaccines are products that produce immunity to
response information needs (2.2.2), and biological threats specific diseases, preventing the disease from occurring.
and the transportation system (2.2.3). When vaccines are available, they must be administered
before the onset of disease symptoms to be effective. An-
2.2.1 Fundamentals
tiviral agents can destroy or weaken some viruses and
also may be helpful for some viral diseases (e.g., small-
This section provides background information for better pox and possibly some hemorrhagic fevers). However,
understanding of biological threats. The fundamentals ad- in many cases, the treatment for viral diseases is limited
dressed below are to supportive care.
· Biological toxins are non-living chemicals produced
· Basics, by living organisms, in contrast with the human-
· Events, manufactured toxins discussed in the chemical threats
· Dose and infectivity, section. Examples are ricin, from the castor bean
· Categories, plant, botulina from the bacteria Clostridium botu-
· Detection, and linum, and mycotoxins from fungi (i.e., molds). Many
· Decontamination. biological toxins are relatively stable.
Diseases from some biological toxins can be treated
More information on biological threats is available from with antitoxins (i.e., botulism), but these are not available
many commonly available sources, including the Internet. for others (i.e., mycotoxins and ricin). In these cases,
treatment is limited to supportive care.
Basics Biological organisms are given a two-part name, where the
first name represents the genus and the second name is unique
There are three general types of biological threat to the species. There can be different versions or strains of the
agents: bacteria, viruses, and toxins produced by biologi- same species. Often, the ability of an organism to infect peo-
cal organisms. ple easily requires only a different strain. Different strains of
the same type of organism also may have different resistance
· Bacteria are single-celled organisms that have a cell to antibiotics.
wall, cell membrane, and DNA found throughout the A wide variety of biological threat lists circulate
cell, rather than in a compartment (i.e., they do not have throughout the government and medical communities.
a nucleus, as in plant and animal cells). Bacteria repro- These lists contain the same disease-causing organisms and
duce by division and are commonly cultured in broth or toxins of typical concern, with variation in the inclusion of
on a nutrient gel. When bacteria establish themselves agents thought to be less likely to be used in an attack.
and replicate in the human body they can cause disease. Table 2-7 lists some commonly considered bioterrorism
Some bacteria can form spores. Bacterial spores have agents, the diseases they cause, and their Center for Disease
extremely tough outer coatings that allow them to sur- Control (CDC) categories, which are described below in
vive in hostile environments in an inactive state, similar "Categories."
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TABLE 2-7 Potential Biological Terrorism Agents
CDC
Agent Type Organism Name Disease Caused Host Organism
Category
Bacillus anthracis A Anthrax Human/Livestock
Bacterial
Coxiella burnetii B Q-fever Human/Insects
spore
Brucellae spp. B Brucellosis Human/Animals
Yersinia pestis A Plague, bubonic and Human/Insects
Vegetative pneumatic
bacteria Burkholderia mallei B Glanders Human/Livestock
Francisella tularensis A Tularemia Human/Insect/Animals
Variola major Filoviruses A Smallpox Human
and Arenaviruses (Ebola, A Hemorrhagic Fevers Human/Insects/Animals
Virus Marburg, Lassa)
Foot and Mouth Virus NA Foot and Mouth Disease Livestock
Toxin Clostridium botulinum A Botulism NA*
produced by Castor bean B Ricin NA*
organisms Various Funji A Mycotoxin toxicity NA*
NA = not applicable. Biological toxins are produced by organisms, but are chemicals rather than living organisms,
hence they do not have a host. All listed toxins are toxic to humans
The potential for exposure is defined as the probability of Events
an individual to be exposed to the agent. Susceptibility refers
to the likelihood of an agent to cause disease in a population Responses to biological events are driven primarily by the
exposed to the agent. type, quantity, and dispersion of the biological agent. Recog-
Persistence of a biological agent relates to how long it re- nition of the types of possible biological events can help in
mains a danger and how difficult it is to render harmless. As assessing vulnerabilities and risk. Three general types of
with chemical agents, the persistence of an agent in the en- biological events are as follows:
vironment depends on factors such as temperature, humidity,
and sunlight. The persistence of a biological agent may be · Natural spread of a disease caused by a biological agent
quite different in the air, versus on surfaces or in soil or not deliberately concentrated as a weapon or for re-
water. In this report chemical agents that substantially de- search purposes. SARS, West Nile Virus, Hong Kong
grade in open air within 24 hours of release were defined as Flu, and Avian Bird Flu are recent examples of biolog-
non-persistent. However for biological agents, the definition ical threats that have not been deliberately concentrated.
of non-persistent is extended to 48 hours because, for the bi- Influenza viruses, which cause the flu, are the biologi-
ological agents addressed, persistence in open environments cal group generally thought to pose the greatest risk of
is either 48 hours or less, or a week or more, making a greater natural spread caused by their ability to continually mu-
distinction between persistence categories delineated by 48 tate into new strains, thereby making established vac-
hours. For non-persistent biological agents in particular, sur- cines ineffective. One of the most extreme influenza
vival is often substantially longer in soils than in open air. outbreaks recorded was in 1918.2 Estimates of deaths
Vegetative bacteria and viruses typically are not very persis- worldwide from the 1918 flu outbreak range from 20
tent in an open environment, thus they only present a long- million to 100 million. There is an increased potential
term risk when they are contagious. In contrast, spores are for the promotion of natural spread of disease during
typically very persistent, lasting months to years in an open events with other threat agents (i.e., conventional,
environment. chemical, or radiological) when responses include
Contagiousness refers to the ability of the biological agent to crowding of injured or displaced people, which may en-
be spread from one person to another after it has increased in able the evolution of new, more contagious strains.3
numbers in the initially infected person. Highly contagious
agents can be spread with face-to-face contact, as coughed or
exhaled droplets from infected individuals in a contagious stage 2
In the U.S., deaths from the 1918 influenza outbreak were at least 500,000, repre-
senting 5 percent of the population at that time.
of the disease are inhaled by others. Some highly contagious 3
The crowded conditions of wounded soldiers in WWI are thought to have facilitated
agents may also be transferred to others from touching the skin, the development of the influenza virus that caused the exceptionally deadly 1918 out-
break. It has been suggested that in the previous year, a strain that was not initially very
clothes, or bedding of an infected individual or corpse. During contagious, was more easily spread under extreme crowding of wounded soldiers, in
the most contagious stages of these diseases, infected individ- particular, providing more opportunity for strain evolution. Similarly, Southeast Asian
markets with dense crowding of a wide variety of animals (i.e., poultry and livestock,)
uals tend to be obviously sick and often bed-ridden. Less and people are thought have facilitated viral strain developments that have lead to the
contagious agents may be spread with bodily fluids. more recent threats from Avian Flu and SARS.
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Lack of knowledge prevents new strains from being agents based on their public health effect, dissemination po-
used as a weapon in bioterrorism. tential, public perception of the risk, and the need for spe-
· Release during transport of biological material is the ac- cial preparation to respond adequately to a deliberate attack.
cidental or intentional release of harmful biological ma- The ranking did not include clean-up costs or plant and
terial being shipped within the transportation system. animal pathogens that do not infect people. The resulting
Such material is considered DOT Class 6 material, ranks were used to establish three risk categories: A, B and
"Toxic and Infectious Materials." These materials have C. Category A agents can cause high mortality rates, can be
strict shipping requirements to minimize leakage and re- relatively easily spread either by contagiousness or delivery
lease. Such a release could occur following accidental as a weaponized aerosol, and may have major public health
or deliberate demolition of a carrier through the use of effects. Category B agents are moderately easy to dissemi-
an explosive device. nate and result in a moderate rate of disease and low mor-
· Deliberate release of a biological weapon is a release of tality rates. This category includes the major threats to food
a biological agent with the intent to harm a target. A and water supplies. Category C agents are those that do not
small amount of a biological weapon may be sufficient currently pose a significant bioterrorism threat but could
to have significant effects in enclosed places such as emerge as future threats.
buildings, tunnels, or subways, or within passenger The CDC categories are often referred to in various ref-
compartments of airplane, trains, cruise liners, buses, erences. However, for this report, the primary characteris-
and so forth. Larger amounts are needed for an effective tics of a biological agent that affect the emergency response
outdoor release. Areas with high visibility, large are the agent's persistence in the environment, which helps
crowds, and high economic effect are thought to be the determine the need for decontamination, and the agent's
most likely targets for bioterrorism. contagiousness, which determines the possible need for
quarantines. Quarantines are only considered for highly con-
The most dangerous form of biological weapons agent is tagious agents. Based on contagiousness and persistence,
an aerosol, which is not the natural state of these organisms. the following categories of biological agents are referred to
Much sophistication is required to generate "weaponized" in this report and summarized in Table 2-8:
forms of these agents as found in the anthrax mailings in
2001. Materials legally transported within the transportation 1. High persistence, low contagiousness--These biolog-
system are not weaponized agents and thus are less likely to ical agents take weeks to years to degrade naturally in
remain suspended in air. However, these materials can still the environment, but they are not typically transmitted
contaminate surfaces, causing access restrictions until ap- from person to person. The causative agent of anthrax,
propriately decontamination. the spores of Bacillus anthracis (BA), is the only CDC
Category A organism that falls within this group. De-
pending on the strain, BA may cause death in 85 per-
Dose and Infectivity cent of infected individuals if untreated. For BA, the
dose required for infectivity has been estimated to be
The infectivity of a biological agent is the actual number between 8,000 to 10,000 spores. Lower numbers may
of inhaled organisms necessary to generate an infection. be required for cutaneous (open wound, skin infec-
These numbers are generally presented as the infectious dose tions) or gastrointestinal forms of the disease. After
(i.e., number of organisms) required for 50 percent of those washing to remove spores from skin and removal of
individuals exposed to become infected (abbreviated ID50). contaminated clothing, it is difficult to transfer an in-
In contrast, contagiousness refers to how easily an infectious fective dose of BA. The causative agent of Q-fever,
agent can be spread from person to person. Infectivity, or Coxiella burnetii, is also a bacterial spore, and a CDC
ID50, can be more clearly measured than contagiousness. Category B agent that typically does not cause death.
Therefore, many experts refer to infectivity rather than con- For Coxiella burnetii, the dose required for infectivity
tagiousness. Agents that cause highly contagious diseases may be as low as one spore. Bacterial spores of both
often have low infectivity; however, not all agents with low agents may last months to years in the environment.
infectivity are highly contagious. The infectivity and conta- The causative agents of brucellosis, several bacterial
giousness of different biological agents are commonly used species of the genus Brucella, are CDC Category B
to define categories of these agents. agents that typically do not cause death. Brucella is not
able to form spores, but is relatively stable in the
environment and can survive up to 6 weeks in dust.
Categories Brucella is relatively easy to decontaminate, while bac-
terial spores can be very difficult to decontaminate be-
The Centers for Disease Control (CDC) assembled a cause of their protective spore coat. Of the toxins in this
panel of experts in 1999 to rank potential biological terror group, mycotoxins (produced by molds, e.g., T2 or
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TABLE 2-8 Biological Threat Groups
PERSISTENCE (and CDC categories in parentheses)
CONTAGIOUSNESS LOW = HIGH =
Less than 2 days in an open environment Weeks to years in an open environment
Bacterial Diseases: Bacterial Diseases:
Tularemia (A) Anthrax (A)
LOW = Plague, bubonic (A) Q-fever (B)
Unlikely person to Glanders (B) Brucellosis (B)
person transmission Toxin Diseases: Toxin Diseases:
Botulism (A) Mycotoxins (A)
Ricin (B)
Bacterial Diseases:
Plague, pneumonic (A)
HIGH = *** Viral Diseases: **
Likely person to person Smallpox (A) None known
transmission Hemorrhagic fevers (A)
Influenza (no CDC category)
Foot-and-mouth* (no CDC category)
* Foot-and-mouth is highly contagious among livestock, it does not cause disease in people.
** Persistence may be longer on surfaces, clothing, and bedding.
*** Note: highly contagious agents can remain persistent within the population regardless of persistence in open
environments
yellow rain) are very difficult to decontaminate, while very contagious, the same causative bacteria can also
ricin (extracted from castor beans) is relatively easy to cause the pneumonic plague, which is very contagious
decontaminate. and listed in the group below.5 If untreated, diseases in
2. Low persistence, low contagiousness--Bacteria and this group may cause death in 33 percent (i.e., tularemia)
toxin in this group cannot survive in the open environ- to 100 percent (i.e., glanders) of the affected population.
ment for more than a couple of days. Many of the As few as a dozen organisms may be sufficient to cause
bacteria in this group last only a few hours in open air, an infection in a person, but these infections can be ef-
while botulinum toxin may take a couple of days to sub- fectively treated with antibiotics.
stantially degrade depending on specific conditions (i.e., 3. Low persistence, high contagiousness--The combina-
it may be stable for weeks in non-moving water or food). tion of high contagiousness and high lethality makes the
Both bacteria and toxins in this group are relatively easy agents in this category formally listed as or equivalent to
to decontaminate. The bacteria in this group are rela- CDC Category A.6 The causative agent of smallpox, Or-
tively infectious, generally needing only 10 to 100 or- thopox virus Variola major, is usually transferred from
ganisms to cause an infection, and include both CDC person to person in airborne droplets from the infected
Category A agents (i.e., causative agents of the bubonic person's coughing or breathing. It may also be trans-
plague and tularemia) and Category B agents (i.e., ferred through skin sores, secretions, and contaminated
causative agents of glanders4). Botulinum toxin is pro- clothing and bedding. Some of the hemorrhagic fever
duced by the bacterium Clostridium botulinum under viruses (e.g., Ebola, Lassa, and Marburg), Yersinia pestis
special conditions such as in poorly prepared canned in pneumonic plague cases, and influenza viruses may
goods and fish products. One of the most poisonous sub- also be readily transferred from person to person.
stances known to man, it is a CDC Category A agent. As Weaponized versions of smallpox, hemorrhagic fever
with other diseases caused by toxins, botulism is not con- viruses, or Yersinia pestis would likely be formulated for
tagious. The contagiousness of bacterial diseases in this
group is relatively low. The bubonic plague is caused by 5
Yersinia pestis can be transmitted through flea bites to infect human lymph nodes,
Yersinia pestis. Although this disease is generally not causing the bubonic plague, which is not easily transmitted to another person because
the bacteria reside in the lymph nodes rather than in the lungs. In contrast, if the same
organism infects the lungs, it causes the pneumonic plague, which can be readily trans-
ferred through person-to-person contact with exhaled droplets making it highly conta-
4
The summary references on glanders used in this report provide conflicting infor- gious. A bioweapon would likely disperse Yersinia pestis as an aerosol, allowing in-
mation on stability in an open environment. Glanders-causing agent Burkholderia halation and causing pneumonic plague.
mallei is reported to be sensitive to UV light by Acquista (The Survival Guide: What 6
The CDC Categories A, B, and C were developed for bioterror agents that infect
to do in a Biological, Chemical, or Nuclear Emergency. 2003, Random House Trade people. The influenza viruses pose a natural spread risk rather than a bioterror risk, and
Paperbacks, NY, p. 28), likely causing its rapid degradation outside. However, it is as such, have not been formally assigned to a CDC bioterror category. However, based
listed as "very stable" in The National Academies Fact Sheet on Biological Attack, on statistics from the 1918 influenza outbreak, lethality may approach that of smallpox
available at: http://www.nae.edu/NAE/pubundcom.nsf/weblinks/CGOZ-6C2MCR/ (i.e., 30 percent) when a vaccine is not available, suggesting equivalence to CDC
$file/Biological%20Attack.pdf. Category A for some influenza strains.
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inhalation. All agents in this group are relatively easy to limitations, but used together can result in sensitive detection
decontaminate in the open environment. For livestock, with a high degree of confidence.
the foot-and-mouth disease is caused by a highly conta- Some antibody identification methods, such as hand held
gious virus. Although this disease is not known to be assays, are relatively simple, single-use devices that require
transferred to people, it could cause substantial eco- little in the way of maintenance other than proper storage
nomic disruption. conditions. The sensitivity of antibody-based identification
technologies depends on the availability of sensitive and
At this time, no commonly recognized biological threat specific antibody reagents. The most well-known type of
agents are both very persistent in an open environment and antibody-based identification in the biodefense market is
very contagious. Also, for the purpose of this study we have hand held immuno-chromatographic assays (HHAs), also
included Foot and Mouth Virus (FMV) as an agroterrorism referred to as antibody "tickets." In general, HHAs are
threat that is highly contagious but not persistent. Recent designed for one agent identification per assay. Although the
events in Taiwan and the United Kingdom have demon- systems are relatively robust, they are not as sensitive as
strated the severe negative economic effect of an FMV out- DNA amplification-based identification systems. These sys-
break among livestock. This virus is highly contagious tems are commercially available and provide a responder
among livestock and sufficiently stable in the environment to with rapid, onsite analysis of some biological agents.
travel many miles through the air to infect other hosts. DNA identification methods use an organism's genetic code
for positive identification. These methods require substantial
operator training and maintenance requirements. DNA-based
Detection and Identification anthrax identification systems are in the early stages of opera-
tion at select U.S. postal facilities. DNA identification for a
The terms "detection" and "identification" are frequently wider variety of materials requires more procedural develop-
interchanged in the context of biological warfare compounds, ment. Specific biological toxins are identified with mass
even though they have very different meanings. Detection of spectrometry, which requires substantial operator training and
biological agents refers to the ability to discriminate between maintenance. Use of these technologies for laboratory or con-
biological and non-biological material without further char- firmatory analysis of samples from the transportation system
acterization. Not all biological materials are hazardous and would likely either be contracted from a commercial firm or be
these technologies do not discriminate between "good" and conducted by another government agency.
"bad" biological organisms. Identification is the ability to dis- None of the identification technologies can determine if
criminate between biological materials and accurately name a biological agent is alive or dead, and a dead bacterium
them. The difference between detection and identification is or virus cannot cause infection. A live agent is confirmed
the degree of resolution. by its ability to grow in a culture media; such growth may
Biological detection technologies detect the presence of take several days. The ability to discriminate between live
airborne biological particles in a sampled volume of air. and dead agents is critical for verifying decontamination
Changes in the number and types of particles in the air may technologies.
indicate the presence of a biological hazard. Generally these
detection technologies can discriminate bacteria and spores
from pollen and fungi also present in the atmosphere. These Decontamination
detectors either use measurement of induced fluorescence,
generally from protein components characteristic of a biolog- Decontamination is the inactivating or killing of bacteria,
ical organism, or the identification of adenosine triphosphate viruses, or toxins. Spores represent the most significant inac-
(ATP) that is indicative of a living biological organism. The tivation challenge. Vegetative bacteria and viruses are rela-
fluorescent detection technology is more sensitive than ATP tively susceptible to many means of remediation. Toxins have
detection, but it cannot discriminate between live and dead or- varying degrees of resistance, but can be inactivated by many
ganisms. Detectors that discriminate live and dead particles of the materials used for decontamination. Surface deconta-
are relatively expensive and do not discriminate between mination of most biological agents can be achieved using dis-
"good" and "bad" organisms, so are subject to false or nui- infecting solvents, foams, gels, or emulsions. A 0.5 percent
sance alarms. These systems serve as "triggers" to activate an hypochlorite solution (i.e., 1 part household bleach, 9 parts
identification system. Detection systems can provide a first water) is a common recommendation. Line-drying clothes in
level of response in a transportation surveillance system. the sun allows ultraviolet rays to kill most organisms. The use
Biological identification technologies are used to name of disinfectant foams can increase the time a surface is ex-
the type of biological material detected. The most common posed to effective concentrations of a disinfectant, which in-
approaches to biological identification are antibody-based creases the likelihood of destroying the biological agent--a
assays and nucleic acid (i.e., DNA) amplification and identi- particular concern for more persistent agents (e.g., anthrax
fication assays. Each of these technologies has benefits and spores and mycotoxins). Mycotoxins are the most difficult of
