Bioterrorism

Published on 10/03/2015 by admin

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Chapter 37 Bioterrorism

Sarah Mooney, MBBCh, MRCP , Christopher Grace, MD, FACP

1 What is the definition of bioterrorism?

A bioterrorism attack has been defined by the Centers for Disease Control and Prevention (CDC) as “the deliberate release of viruses, bacteria or other agents used to cause illness or death in people, animals or plants.” An attack would most likely be occult and have occurred days to weeks before the first patients presenting to the intensive care unit (ICU). Many of the agents are contagious via person-person spread, which may lead to secondary and tertiary waves of ill patients over weeks to months. The intent of an attack is not only to cause significant morbidity and mortality but also to spread terror and panic throughout the population.

2 What are some possible agents that might be used in an attack?

The CDC classifies six pathogens as class A bioterrorism agents: smallpox, plague, botulism, tularemia, viral hemorrhagic fever (VHF), and anthrax. These agents are considered to have the greatest potential for mass casualties, large-scale dissemination, and public panic and social disruption. All of them except VHF have been developed as biological weapons. They are stable in aerosol form and would be most likely delivered in this manner. Most of the civilian population remains susceptible to them, and most cause illnesses not typically seen by providers, causing delayed or missed diagnoses. The major clinical syndromes are summarized in Table 37-1.

Table 37-1 Category a Bioterrorism Agents

3 What are clues to a biological attack?

Recognition of a biological attack may be delayed until patients begin accessing medical care, which may be days to weeks after the event depending on the incubation period of the pathogen (Table 37-1). Features that might suggest a biological attack include the following:

Any unusual increase or clustering of patients being seen with clinical symptoms that suggest an infectious disease outbreak

A suspected or confirmed communicable disease in a nonendemic area, for example, plague in New England

An unusual age distribution of a common disease

An unusual temporal and/or geographic clustering of illness, for example, persons who attended the same ball game or parade

Simultaneous outbreaks in humans and animals (all class A agents with the exception of smallpox infect animals)

An unusual seasonal distribution of illness, for example, influenza-like symptoms in summer

4 What pathogens would present with respiratory failure?

Anthrax: Pneumonic anthrax is caused by the inhalation of the spore form of Bacillus anthracis. It begins as a nonspecific influenza-like illness with fever, cough, malaise, headache, and vomiting. Rapid progression occurs to hemorrhagic mediastinitis, hilar lymph node enlargement, respiratory failure, hemodynamic collapse, and death. Although chest radiographs classically show only a widened mediastinum without pulmonary infiltrates, several of the victims from the anthrax letter attacks in the fall of 2001 did have pulmonary infiltrates and pleural effusions. Bacteremia and meningitis can occur.

Plague: Pneumonic plague, caused by Yersinia pestis, can develop secondarily from bubonic plague via hematogenous dissemination from involved lymph nodes or primarily from inhalation of the plague bacillus. Patients are seen with the sudden onset of headache, fever, shortness of breath, cough, and hemoptysis. Chest radiographs most often reveal bilateral bronchopneumonia. There may be leukocytosis, disseminated intravascular coagulation (DIC), and elevated liver function test results. Rapid progression to respiratory failure and shock ensues.

Tularemia: If Francisella tularensis is inhaled, a syndrome similar to community-acquired pneumonia develops with fever, myalgias, headache, pleuritic chest pain, and a dry cough. Concomitant pharyngitis may be present. Some patients demonstrate a pulse-temperature deficit, where an increase in temperature is not accompanied by a relative increase in heart rate. Chest radiographs may have a variety of findings including unilateral or bilateral pneumonia, hilar lymphadenopathy, pleural effusions, and, less often, parenchymal cavitation.

5 What pathogens would present with shock?

Anthrax and plague may present with shock coupled with pneumonia and respiratory failure.

VHF can be caused by a diverse group of RNA viruses including Ebola, Marburg, Lassa fever, and Rift Valley fever from sub-Sahara Africa, in addition to Junin virus, Machupo virus, Guanarito virus, and Sabia virus from South America. These are all capable of causing a wide spectrum of illness ranging from asymptomatic to life threatening. As the name implies, these viruses cause fever and a bleeding diathesis. Patients typically are seen with an acute febrile illness associated with headache, fatigue, myalgias, abdominal pain, diarrhea, rash, pharyngitis, and hypotension. Bleeding can range from mild conjunctival hemorrhage to severe mucocutaneous bleeding. Progression to shock occurs in severe cases, and patients typically die of septic shock rather than blood loss.

6 What pathogens would present with paralysis?

Botulism is caused by a toxin released by Clostridium botulinum. The toxin may be ingested from infected food or released from bacteria infecting a wound. Botulism presents as a progressive paralysis, which begins with the bulbar musculature and descends to the extremities and trunk. Typical initial symptoms include diplopia, ptosis, dilated pupils, facial weakness, dysarthria, and dysphagia. Over hours to days, the paralysis descends to the arms, the diaphragm resulting in respiratory failure, and finally the legs. Features that are not consistent with botulism are extremity weakness without bulbar weakness, impaired consciousness, fever except when an aspiration pneumonia has developed, or sensory abnormalities.

7 What pathogens may present with predominantly cutaneous manifestations?

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