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23 passenger transport system (i.e., aviation, mass transit, and fer- between exposures to biological agents to onset of symptoms ries) could have a devastating effect on customers riding the is often several days. This is also confounded by the fact that system. Substantial delays would occur attempting to locate the many of these diseases initially present with flu-like symp- source. The most devastating medical effect would result from toms, which can add days to the correct diagnosis. Further- the release of contagious agents. By the time the infections more, the later detection and identification occur, the greater were discovered, there would be many more foci of infection. the sampling and analysis needed to find out the extent of the The protected environment of enclosed spaces would help pre- contamination. Labile agents such as viruses and vegetative serve biological agents, and decontamination efforts may be bacteria may escape detection because of their instability in applied in these areas regardless of the agent's persistence in the environment. order to assure safety and public confidence. More persistent agents would require more extensive and time-consuming de- contamination measures. 2.2.4 Consequence Minimization The confined nature of ships and the sequestration of the personnel can, in some cases, minimize a biological agent's A primary factor in minimizing the consequences of a bi- effect as occurred with the Norwalk virus incidents. Then, ological release is the delay between the actual event and the incubation period was short enough for individuals to the discovery that a biological release has occurred. For all become ill while still confined to the ship. This is in con- biological agents, the sooner a release has been determined, trast to a biological release in the transit, rail, and aviation the fewer the number of casualties. Although this differen- modes, where the transit time is almost always less than the tial varies widely between categories, it still is a factor. time required for observable symptoms, and passengers de- Once an event has been identified, it must be characterized barking at subsequent stops can serve as secondary sources so that protective and restoration actions can be initiated. of contamination. Cargo transport of agricultural products Characterization includes identifying the agent and the es- and livestock are another potential target for bioterrorism. tablishment of the contaminated area. Organisms with low Release of a highly contagious virus such as the foot and persistence may no longer be detectable in the environment mouth virus could spread the contamination widely with by the time a release has been determined, while stable devastating economic effects. If a transportation mode is spores in weaponized formulations will pose a continued contaminated from either an enclosed release or an outdoor health hazard as they are re-suspended by air currents. The release, intersecting modes of transportation can cross- size and variable environments in the transportation system contaminate each other. present both strengths and vulnerabilities in terms of de- A large outdoor release may result in closing transporta- fense against biological attacks. tion paths in the vicinity and downwind of the release site If a biological agent is released in an enclosed space (i.e., until the limits of dispersion are established. In such an event, building or passenger compartment), the HVAC systems may vehicle and building windows and HVAC systems should be be closed or redirected to prevent continued re-circulation of closed so as to prevent exchanging air with the outside. The particles. This action would be the same for chemical and ra- duration of risks associated with aerosols may be extended in diological threats, thus an agent need not be identified to initi- areas with traffic-induced winds that can re-suspend particles ate this response. If a release occurs outside, building HVAC into the atmosphere. systems may be set to have slightly positive pressure inside, All biological agents would have similar effect during the thus reducing the ability for outside contaminants to enter the early phase after a release, however, the duration of the haz- building. Once again, this action would be the same for chem- ard varies with the agent's persistence. Decontamination of ical and radiological threats, so an agent need not be identified viruses and vegetative bacteria may occur rapidly (i.e., hours to initiate this response. The incorporation of HEPA filtration to days) in the environment in the absence of secondary sta- within enclosed transportation facilities will greatly enhance bilization additives. Stabilizing agents can extend the life of the rapid removal of the threat from the environment. these agents several-fold. The stability of different biologi- For rapid response in the event a threat agent is suspected in cal toxins varies from days to years in the environment. In association with an explosion, emergency response plans may contrast, bacterial spores (i.e., BA) are stable for years in the specify an immediate, conservative radius surrounding the ex- outside environment. In their natural form, these agents are plosion site for isolation until the agent is identified and the quite stable and long-lived in the environment. The formula- most appropriate response can be determined. These bound- tion as a weaponized agent requires total decontamination aries may be adjusted after a more complete biological survey because of the ability of these preparations to re-suspend into with surface sampling and identification of the released agent. the air and pose a health hazard. A difficult and probably controversial aspect of determining In all cases of biological agent release, timely detection transportation response goals will be in establishing the physi- and identification of the threat is important for developing cal boundaries of isolation areas. Transportation officials are the most appropriate and effective response. Unlike chemi- unlikely to have primary responsibility for these decisions cal agents that react within seconds to hours, the delay and probably will be following instructions from incident