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Bioterrorism

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Community Nurses on the Front Lines

Recent terrorist attacks against the United States has put everyone on the alert. We now realize the United States is vulnerale to terrorism and in many ways we are not prepared. September 11, 2001 found the nation unprepared and devastated by the attack on the World Trade Centers in New York and the Pentagon in Washington D.C. One of the more serious forms of terrorism that could cause catastrophic epidemics involves the use of biologic weapons. As health care workers it is essential that we know about the pathogens that are most likely to be used as weapons: anthrax, botulinum toxin, tularemia, smallpox, viral hemorrhagic fevers and pneumonic plague. Community Nurses are on the front lines of this potential threat!

What is 'bioterrorism' ?
Bioterrorism is the overt or covert dispensing of disease pathogens by individuals, groups, or governments for the expressed purpose of causing harm for either ideological, political, or financial gain

CDC Bioterrorism Agent Classification System

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The Centers for Disease Control (2004) have placed agents in one of three priority categories for initial public health preparedness efforts: A, B, or C. Agents in Category A have the greatest potential for adverse public health impact with mass casualties, and most require broad-based public health preparedness efforts (e.g., improved surveillance and laboratory diagnosis and stockpiling of specific medications). Category A agents also have a moderate to high potential for large-scale dissemination or a heightened general public awareness that could cause mass public fear and civil disruption.

Most Category B agents also have some potential for large-scale dissemination with resultant illness, but generally cause less illness and death and therefore would be expected to have lower medical and public health impact. These agents also have lower general public awareness than Category A agents and require fewer special public health preparedness efforts. Agents in this category require some improvement in public health and medical awareness, surveillance, or laboratory diagnostic capabilities, but presented limited additional requirements for stockpiled therapeutics beyond those identified for Category A agents. Biological agents that have undergone some development for widespread dissemination but do not otherwise meet the criteria for Category A, as well as several biological agents of concern for food and water safety, are included in this category.

Biological agents that are currently not believed to present a high bioterrorism risk to public health but which could emerge as future threats (as scientific understanding of these agents improves) were placed in Category C. These agents are considered as part of ongoing public health infrastructure development for detecting and addressing emerging infectious diseases ( CDC, 2004).

Category A Agents

  • Can be easily disseminated or transmitted person to person
  • Cause high mortality with a potential for major public health impact
  • Might cause public panic and social disruption.
  • Require special action for public health preparedness

Category B Agents

  • Are moderately easy to disseminate
  • Cause moderate morbidity and low mortality
  • Require specific enhancements of diagnostic capacity and disease surveillance.

Category C Agents

  • Include emerging pathogens that could be engineered for mass dissemination in the future because of:
    • Availability
    • Ease of production and dissemination
    • Potential for high morbidity and mortality and major health impact

Although use of conventional weapons such as explosives or firearms is still considered the most likely means by which terrorists could harm civilians, experts believe that there is an increasing risk and probability for the use of biological or chemical weapons. Public health agencies must prepare for the large-scale incident that would undoubtedly lead to catastrophic public health consequences. The selection and prioritization of the potential biological terrorism agents described by the Centers for Disease Control in Article 2, were not based on the likelihood of their use, but on the probability that their use would result in an overwhelming adverse impact on public health (CDC, 2004).

Have biological weapons ever been used in warfare or terrorism?
Yes. In warfare, from Persia in the 6th century BCE to the modern Iran-Iraq conflict of the 20th. And even in the civilian public sector, the more notable event occuring in September 1984 when the Rajneesh cult outside of Antelope, Oregon was said to have contaminated salad bars in local restaurants in The Dalles, Oregon, with Salmonella typhi (typhoid), resulting in the poisoning of 750 people, in order to "influence the outcome of a local election".

Anthrax Anthrax is primarily a disease of domesticated and wild animals, particularly herbivorous animals, such as cattle, sheep, horses, mules, and goats. Humans become infected incidentally when brought into contact with diseased animals, which includes their flesh, bones, hides, hair and excrement.

The natural history of Bacillus anthracis is obscure. Although the spores have been found naturally in soil samples from around the world, the organisms cannot be regularly cultivated from soils where there is an absence of endemic anthrax. In the United States there are recognized areas of infection in South Dakota, Nebraska, Arkansas, Texas, Louisiana, Mississippi and California; small areas exist in other states. Even in endemic areas, anthrax occurs irregularly, often with many years between occurrences.

In humans, anthrax is fairly rare; the risk of infection is about 1/100,000. The most common form of the disease in humans is cutaneous anthrax , which is usually acquired via injured skin or mucous membranes. A minor scratch or abrasion, usually on an exposed area of the face or neck or arms, is inoculated by spores from the soil or a contaminated animal or carcass. The spores germinate, vegetative cells multiply, and a characteristic gelatinous edema develops at the site. This develops into papule within 12-36 hours after infection. The papule changes rapidly to a vesicle, then a pustule (malignant pustule), and finally into a necrotic ulcer from which infection may disseminate, giving rise to septicemia. Lymphatic swelling also occurs within seven days. In severe cases, where the blood stream is eventually invaded, the disease is frequently fatal.

Smallpox Smallpox had two main forms: variola major and variola minor. The two forms showed similar lesions. The disease followed a milder course in variola minor, which had a case-fatality rate of less than 1 per cent. The fatality rate of variola major was around 30%.

There are two rare forms of smallpox: haemorrhagic and malignant. In the former, invariably fatal, the rash was accompanied by haemorrhage into the mucous membranes and the skin. Malignant smallpox was characterized by lesions that did not develop to the pustular stage but remained soft and flat. It was almost invariably fatal.

There is no animal reservoir. Insects play no role in transmission. Smallpox is transmitted from person to person by infected aerosols and air droplets spread in face-to-face contact with an infected person after fever has begun, especially if symptoms include coughing.

In the past, patients suffering from variola major (the more severe form of the disease) became bedridden early (in the phase before the eruption of rash) and remained so throughout the illness. Spread of infection was limited to close contacts in a small vicinity.

Plague Plague is a zoonosis involving rodents and their fleas. The causative agent of plague is the bacterium Yersinia pestis . Humans are incidental hosts and are usually infected by the bite of rodent fleas. Plague can also be acquired by direct contact with infectious materials or inhalation of infective respiratory droplets.

Plague continues to be enzootic in wild rodent populations over large rural areas of the Americas, Africa, and Asia, with occasional outbreaks among commensal rodents in villages and small towns. When infection spreads to rats in urban or populated areas, persons are at markedly increased risk of exposure. In the past several decades, however, urban outbreaks have been rare and limited in size.

In recent years, human plague has been reported in Africa from Angola, Botswana, Democratic Republic of the Congo, Kenya, Libya, Madagascar, Malawi, Mozambique, South Africa, Tanzania, Uganda, Zambia, and Zimbabwe; in Asia from Burma, China, India, Kazakhstan, Laos, Mongolia, and Vietnam; and in the Americas from Bolivia, Brazil, Ecuador, Peru, and the United States.

Tularemia Tularemia, or rabbit fever, is a bacterial disease associated with both animals and humans. Although many wild and domestic animals can be infected, the rabbit is most often involved in disease outbreaks. Tularemia is relatively rare in Illinois; five or fewer cases are reported each year.

The disease occurs throughout the United States in all months of the year. The incidence, however, is higher for adults in early winter during rabbit hunting season and for children during the summer when ticks and deer flies are abundant.

Many routes of human exposure to the tularemia bacteria are known to exist. The common routes include inoculation of the skin or mucous membranes with blood or tissue while handling infected animals, the bite of an infected tick, contact with fluids from infected deer flies or ticks, or handling or eating insufficiently cooked rabbit meat. Less common means of spread are drinking contaminated water, inhaling dust from contaminated soil or handling contaminated pelts or paws of animals. Tularemia is not spread from person to person.

BotulismBotulism is a disease caused by the toxins (poisons) produced by several members of the group of bacteria called Clostridium botulinum . These bacteria are found in soil throughout the world and produce spores that are able to survive in a dormant state until more favorable conditions allow them to grow.

The seven distinct toxins they produce are some of the most deadly substances known. The toxins are designated by the letters A through G, and types A, B, E, and F toxins have produced human disease. Botulinum toxins affect people of all ages by preventing certain nerves from functioning, resulting in muscle paralysis. Because of this action these toxins are designated "neurotoxins."

Botulism in humans is most often the result of eating food containing the toxin. Botulinum neurotoxins are also a serious bioterrorism concern because the toxins are relatively easy to make and deliver and are highly lethal. Unlike infectious diseases, however, botulism cannot be transmitted from one person to another.

Viral Hemorrhagic Fever Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused by several distinct families of viruses. In general, the term "viral hemorrhagic fever" is used to describe a severe multisystem syndrome (multisystem in that multiple organ systems in the body are affected).  Characteristically, the overall vascular system is damaged, and the body's ability to regulate itself is impaired.  These symptoms are often accompanied by hemorrhage (bleeding); however, the bleeding is itself rarely life-threatening. While some types of hemorrhagic fever viruses can cause relatively mild illnesses, many of these viruses cause severe, life-threatening disease.

The Special Pathogens Branch (SPB) primarily works with hemorrhagic fever viruses that are classified as biosafety level four (BSL-4) pathogens (See column left). A list of these viruses appears in the SPB disease information index . The Division of Vector-Borne Infectious Diseases, also in the National Center for Infectious Diseases, works with the non-BSL-4 viruses that cause two other hemorrhagic fevers, dengue hemorrhagic fever and yellow fever.

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Contact Instructor | ©2003 bdamazo@csuchico.edu