Direct Cardiovascular Implications of Emerging Infectious Diseases and Biological Terrorism Threats

Emerging infections are those with a rising incidence over recent decades and those that threaten to increase, encompassing both newly emerging and re-emerging infections. The emergence of a new infectious agent in the population, the new recognition of a previously undetected circulating agent, or the realization that a noncommunicable disease is actually caused by infection contribute to this group of microbial threats, unrelated to any possible intentional release of biologic agents or bioterrorism (1). As with the scope of the larger body of all infections and infectious diseases, the capacity of emerging infections to affect the cardiovascular system varies from none to limited or increased risk. However, this task force report will focus on the possible cardiovascular implications of emerging infectious diseases and infection with select agents designated to have potential for intentional release. A wide range of infectious agents that can emerge in spontaneous epidemics or be disseminated in bioterrorist attacks can affect the cardiovascular system. Many of these infectious agents have caused disease sporadically (e.g., botulism, tularemia) or endemically (e.g., viral hemorrhagic fevers) in certain parts of the world for centuries; others are relative newcomers (e.g., severe acute respiratory syndrome or SARS, Nipah virus). Some of these agents (e.g., smallpox) do not occur naturally at present and even one confirmed case would signal a likely bioterrorist event. When focusing on the select potential agents of bioterrorism, as well as emerging infectious diseases, the clinical syndromes catalogued by the U.S. Department of Health and Human Services are as varied as the pathogens that produce them (2,3). With some, the direct clinical impact is limited to 1 organ system, as in the case of Clostridium botulinum toxin-induced neuroparalytic illness (4). Other agents can affect multiple organ systems, as in the case of Coxiella burnetii infection, which affects both pulmonary and hepatic systems (5). Additional factors accentuate the complexity of bioterrorism-related illnesses. The temporal onset of different clinical manifestations following exposure can vary. For example, Q fever endocarditis is an illness of chronic infection; whereas pneumonia is seen acutely following exposure (5). However, naturally occurring infections with most of the designated bioterrorism agents are rarely seen in the U.S. today. Because of this, many clinicians are unfamiliar with the associated clinical syndromes and may not initially recognize when an illness stems from exposure to one of these agents, much less from intentional release in a bioterrorism attack (6). The Centers for Disease Control and Prevention (CDC) has classified certain diseases and agents into 3 relatively highpriority categories (A, B, and C) (2,3). These diseases and agents are summarized in Tables 1 and 2. Diseases and agents in Category A have the highest priority because they can be disseminated or transmitted easily from person to person, result in high mortality rates, have the potential for major public health impact, may cause public panic and social disruption, and require special action for public health preparedness. Diseases and agents in Category B are moderately easy to disseminate, result in moderate morbidity rates and low mortality rates, and require specific enhancements of the diagnostic capacity and enhanced disease surveillance. Diseases and agents in Category C include emerging pathogens that could be engineered for mass dissemination in the future because of availability, ease of production and dissemination, and the potential for high morbidity and mortality rates and major public health impact. This report focuses on the Category A, B, and C agents, but an unlimited number of other potential, nonbioterrorism, microbial threats exist from natural evolution, transformation, and transmission of existing pathogens, including emerging and re-emerging infectious diseases, as well as from genetically engineered variants or “mosaics” that can multiply the potential transmissibility, morbidity, and mortality of agents released in a terrorist attack. Many of the Category A, B, and C agents injure the myocardium, pericardium, or endothelium by direct infection or infiltration or through a chemical toxin (e.g., ricin). For some, the evidence of direct effects stems from multiple observations. For others, information rests on a single or a small set of anecdotal reports. Although such direct injury could harm even healthy individuals with a previously normal cardiovascular system, the reality is that most of the currently known, high-risk agents are not directed at the cardiovascular