Glossary of Medical Terms
Adapted from Stedman's Electronic Medical Dictionary,
Williams & Wilkins, Baltimore, MD, 1996 and
Principles and Practice of Infectious Diseases,
Mandell et al, Third Edition.

Bacteria are unicellular organisms. They vary in shape and size from spherical cells - cocci - with a diameter of 0.5-1.0 μm (micrometer), to long rod-shaped organisms - bacilli - which may be from 1-5 μm. Chains of bacilli may exceed 50 μm in length. The shape of the bacterial cell is determined by the rigid cell wall. The interior of the cell contains the nuclear material (DNA), cytoplasm, and cell membrane, that are necessary for the life of the bacterium. Many bacteria also have glycoproteins on their outer surfaces which aid in bacterial attachment to cell-surface receptors. Under special circumstances, some types of bacteria can transform into spores. The spore of the bacterial cell is more resistant to cold, heat, drying, chemicals, and radiation than the vegetative bacterium itself. Spores are a dormant form of the bacterium and, like the seeds of plants, they can germinate when conditions are favorable.

The term rickettsia generally applies to very small, gram-negative coccobacillary organisms of the genera Rickettsia and Coxiella. Rickettsiae are unique from classical bacteria in their inability to grow (with rare exceptions) in the absence of a living host cell, but many are susceptible to treatment with antibiotics.

Bacteria generally cause disease in human beings and animals by one of two mechanisms: by invading host tissues, and by producing poisons (toxins). Many pathogenic bacteria utilize both mechanisms. The diseases they produce often respond to specific therapy with antibiotics. It is important to distinguish between the disease-causing organism and the name of the disease it causes (in parentheses below). This manual covers several of the bacteria or rickettsiae considered to be potential BW threat agents: Bacillus anthracis (anthrax), Brucella spp. (brucellosis), Burkholderia mallei (glanders), Burholderia pseudomallei (melioidosis), Yersinia pestis (plague), Francisella tularensis (tularemia), and Coxiella burnetii (Q fever).

Bacterial agents

• Cutaneous Anthrax: Bacillus anthracis
• Pulmonary Anthrax: Bacillus anthracis
• Brucellosis: Brucella spp.
• Glanders and Meliodosis: Burkholderia mallei and Burholderia pseudomallei
• Plague: Yersinia pestis
• Q Fever: Coxiella burnetii
• Tularemia: Francisella tularensis

Viral agents

• Smallpox: Variola major and Variola minor
• Venezuelan Equine Encephalitis (VEE): a species of the Alphavirus genus
• Viral Hemorrhagic Fever
  VHFs are caused by viruses of four distinct families: arenaviruses, filoviruses, bunyaviruses, and flaviviruse

Biological Toxins

• Botulinum: the bacterium Clostridium botulinum
• Ricin: the castor oil plant, Ricinus communis
• Staphylococcal Enterotoxin B: the bacterium Staphylococcus aureus
• T-2 Mycotoxins: a species of fungi

Charts

• BW Agent Characteristics

The ability to determine who is at risk and to make appropriate decisions regarding prophylaxis and other response measures after a biological attack, (whether from bioterrorism or biological warfare on the battlefield), will require the tools of epidemiology. After a successful covert attack, the most likely first indicator will be increased numbers of patients presenting to individual healthcare providers or emergency departments with similar clinical features, caused by the disseminated disease agent. The possibility exists that other medical professionals, such as pharmacists or laboratorians, who may receive more than the usual numbers of prescriptions or requests for laboratory tests may be the first to recognize that something unusual is occurring. Because animals may be sentinels of disease in humans and many of the high-threat bioagents discussed in this book are zoonoses, it is possible that veterinarians might recognize an event in animals before it is recognized in humans. Medical examiners, coroners, and non-medical professionals, such as morticians, may also be important sentinel event reporters.

To help ensure a prompt and efficient response, public health authorities must implement surveillance systems so they know the background disease rates and can recognize patterns of nonspecific syndromes that could indicate the early manifestations of a bioagent attack. The system must be timely, sensitive, specific, and practical. To recognize any unusual changes in disease occurrence, surveil¬lance of background disease activity should be ongoing, and any variation should be followed up promptly with a directed examination of the facts regarding the change. In the past several years, many public health authorities have initiated syndrome-based surveillance systems in an attempt to achieve near real-time detection of unusual events. Regardless of the system, a sudden sharp increase in illness rates, or the diagnosis of a rare or unusual illness may still be first recognized by clinicians or laboratorians.

After detection of a potential disease outbreak, whether natural or human-engineered, a thorough epidemiological investigation will assist medical personnel in identifying the pathogen and lead to the institution of appropriate medical interventions. Identifying the affected population, possible routes of exposure, signs and symptoms of disease, along with rapid laboratory identification of the causative agent(s), will greatly increase the ability to institute an appropriate medical and public health response. Good epidemiologic information can guide the appropriate follow-up of those potentially exposed, as well as assist in risk communication and responses to the media.

Many diseases caused by weaponized bio-agents present with nonspecific clinical features that may be difficult to diagnose and recognize as a biological attack. Features of the epidemic may be important in differentiating between a natural and a terrorist or warfare attack. Epidemiologic clues that may indicate an intentional attack are listed in Table 1. While a helpful guide, it is important to remember that naturally occurring epidemics may have one or more of these characteristics and a biological attack may have none. However, if many of the listed clues are recognized, one’s index of suspicion for an intentionally spread outbreak should increase.

Once a biological attack or any outbreak of disease is suspected, the epidemiologic investigation should begin. There are some important differences between epidemiological investigations for natural and deliberate outbreaks. Because the use of a biological weapon is a criminal act, it will be very important for the evidence gathered to be able to stand up to scrutiny in court. Therefore, if suspected to be intentional, samples must be handled through a chain of custody and there must be good communication and information sharing between public health and law-enforcement authorities. In addition, because the attack may be intentional, one must be prepared for the unexpected – there is the possibility of multiple outbreaks at different locations as well as the use of multiple different agents, including mixed chemical and bio-agents or multiple bio-agents.

The first step in the investigation is to confirm that a disease outbreak has occurred. Because an outbreak has a higher rate of an illness than is normally seen in a specific population, it is helpful to have background surveillance data to determine if what is being seen constitutes a deviation from the norm. For example, in mid-winter, thousands of cases of influenza may not be considered an outbreak, whereas in the summer, it might be highly unusual. In addition, even a single case of a very unusual illness, such as inhalational anthrax, might constitute an outbreak and should be viewed with suspicion. The clinical features seen in the initial cases can be used to construct a case definition to determine the number of cases and the attack rate [the population that is ill or meets the case definition divided by the population at risk]. The case definition allows investigators who are separated geographically to use the same criteria when evaluating the outbreak. The use of objective criteria in the case definition is critical to determining an accurate case number, as additional cases may be found and some cases may be excluded. This is especially true as the potential exists for panic and for subjective complaints to be confused with actual disease.

Once the attack rate has been determined, an outbreak can be described in terms of time, place, and person. These data will provide crucial information in determining the potential source of the outbreak. The epidemic curve is calculated based upon cases over time. In a point-source outbreak, which is most likely in a biological attack or terrorism situation, individuals are exposed to the disease agent in a fairly short time frame. The early phase of the epidemic curve may be compressed compared to a natural disease outbreak. In addition, the incubation period could be shorter than for a natural outbreak if individuals are exposed to higher inocula of the bioagent than would occur in the natural setting. The peak may occur in days or even hours. Later phases of the curve may also help determine if the disease is able to spread from person to person. Determining whether the disease is contagious will be extremely important for determining effective disease control measures. If the agent(s) is released at multiple times or sites, additional cases and multiple sequential peaks in the epidemic curve may also occur, something that happened with the mailed anthrax letters.

Once the disease is recognized, appropriate prophylaxis, treatment, and other measures to decrease disease spread, such as isolation (if needed for a contagious illness) would be instituted. The ultimate test of whether control measures are effective is determined by observation to see if they reduce ongoing illness or spread of disease.

In summary, it is important to understand that the recognition of and preparation for a biological attack will be similar to that for any infectious disease outbreak, but the surveillance, response, and other demands on resources will likely be of an unparalleled intensity. Public anxiety will be greater after an intentionally caused event; therefore, a sound risk-communication plan that involves public health authorities will be vital to an effective response and to allay the fears of the public. A strong public-health infrastructure with an effective epidemiological investigation capability, practical training programs, and preparedness plans are essential to prevent and control disease outbreaks, whether they are naturally occurring or intentional.

Table 1. Epidemiologic Clues of a biowarfare or Bioterrorist Attack

• The presence of a large outbreak with a similar disease or syndrome, especially in a discrete population
• Many cases of unexplained diseases or deaths
• More severe disease than is usually expected for a specific pathogen or failure to respond to standard therapy
• Unusual routes of exposure for a pathogen, such as the inhalational route for diseases that normally occur through other exposures
• A disease case or cases that are unusual for a given geographic area or transmission season
• Disease normally transmitted by a vector that is not present in the local area
• Multiple simultaneous or serial epidemics of different diseases in the same population
• A single case of disease caused by an uncommon agent (smallpox, some viral hemorrhagic fevers, inhalational anthrax, pneumonic plague)
• A disease that is unusual for an age group
• Unusual strains or variants of organisms or antimicrobial resistance patterns different from those known to be circulating
• A similar or exact genetic type among agents isolated from distinct sources at different times or locations
• Higher attack rates among those exposed in certain areas, such as inside a building if released indoors, or lower rates in those inside a sealed building if released outside
• Outbreaks of the same disease occurring simultaneously in noncontiguous areas
• Zoonotic disease outbreaks
• A zoonotic disease occurring in humans, but not animals
• Intelligence of a potential attack, claims by a terrorist or aggressor of a release, and discovery of munitions, tampering, or other potential vehicle of spread (spray device, contaminated letter)

Print a copy of the emergency contact numbers to include in a safety binder or on a lab bulletin board.

National Response Center: (for chem/bio hazards & terrorist events)	1-800-424-8802
National Domestic Preparedness Consortium: (for civilian use)	1-225-578-8187
FEMA Center for Domestic Preparedness	1-866-213-9553
USAMRIID's Emergency Response Line:	1-888-872-7443
CDC'S Emergency Operations Center: (for health professionals and government officials)	1-770-488-7100
US Army Chemical Materiel Agency Operations Center	1-410-436-4484 or DSN 584-4484