Introduction

Field hospitals can play a key role in the clinical treatment and public-health management of infectious diseases during various emergency situations. An infectious disease outbreak itself may in fact represent the reason for the establishment of a field hospital and the facility’s primary mission may be directly related to that specific infectious disease; that is, an infectious disease disaster. Such was the case for many field hospitals established as Ebola treatment units (ETU)s in the 2014–2015 public health emergency of international concern associated with the epidemic of Ebola virus disease (EVD) in Western Africa[1–5]. This same scenario can effectively occur with other contagious pathogens, which lead to epidemics or pandemics that overwhelm established health-care systems in various parts of the world (e.g., a regional epidemic of cholera or pandemic influenza). This scenario is not likely to be unique to sub-Saharan Africa or even isolated to solely lower resourced countries. The same considerations for setting up field hospitals in the context of an overwhelming contagious disease outbreak may become necessary in the developed world, as well.

More commonly in other disaster scenarios, a field hospital is established for reasons unrelated to infectious disease, primarily. These include emergency situations caused by war and conflict, natural disaster, famine, population movements, and resettlement: all of which may, and often do, manifest outbreaks of infectious diseases as secondary concerns.

Infectious Diseases in Emergencies

Within the emergency phase of crises, and not uncommonly in periods of recovery from disaster, morbidity and mortality rates can surge because of infectious diseases, with over half of the mortality in refugee situations, for example, caused by measles, diarrheal diseases, acute respiratory infections, and malaria[6]. Refugee populations are at higher risk for outbreaks of many diseases including measles, cholera, shigellosis, meningitis, and typhus[6].

The conditions following acute and chronic disasters often include displaced populations, compromised water supplies and sanitation, nutritional vulnerability, and limited access to health-care services including diminished access to immunizations[7]. Disasters routinely influence the personal hygiene practices of a population and can result, secondarily, in wounds and injuries that become infected (via tetanus, Staphylococci, Streptococci, waterborne organisms such as Aeromonas, Vibrio and Pseudomonas species)[8]. Diseases often occur at a higher rate in the wake of disasters due to these other environmental conditions, such as infections resulting from contaminated food and water, including cholera, diarrheal diseases, hepatitis A, hepatitis B, parasitic diseases such as amebiasis, cryptosporidiosis, and giardiasis, rotavirus, shigellosis, and typhoid fever[8]. Animal bites (leading to secondary infections, including rabies) as well as vector-borne diseases could be of concern, including West Nile virus, encephalitis, dengue, Zika, and malaria[8]. Diseases associated with crowding such as measles, meningitis, and acute respiratory infections can also be major issues of concern in the field-hospital setting[7]. Exposure to dead bodies in the midst of disaster is usually not a source of outbreaks of disease, although exposure to blood-borne and other bodily fluid-related pathogens for those handling corpses is a potential concern and precautions need to be taken[7]. This was a significant element needing to be addressed by field hospitals throughout the Ebola crisis in West Africa. Generally, infection control practices can be a challenge in any field-hospital environment, with a broad range of issues needing to be addressed to include those associated with field-hospital design, the placement of patients, food and water supplies, waste disposal, toileting, and vector and pest control[9,10].

Planning

There are numerous considerations that need to be entertained in planning for the deployment of a field hospital under any circumstances during crises or following disaster. There is no such thing as the routine deployment of a field hospital, but in planning for operations under conditions associated with a high threat of a contagious pathogen there are even more extraordinary considerations that must be addressed. Site selection and the characteristics of the facility to be employed, as well as expertise and training of personnel are several issues that are normally looked at when mobilizing a field hospital to provide surge capacity in crises. These issues are of no less concern in an epidemic scenario and may, in fact, require added scrutiny. Additionally, issues related to medical intelligence (e.g., epidemiology of disease, bioterrorism threats), information sharing, and risk communications all may be heightened concerns to build into the planning for circumstances related to an epidemic outbreak, which may not be part of more typical planning cycles in preparation for mobilizing a field hospital[11].

Site selection for the deployment of a field hospital for any purpose and under any conditions demands attention to many details. Vehicle and pedestrian access, proximity to the population served, and vulnerability to flooding are examples of the many generic concerns that must be addressed in planning. When considering the location for a field hospital in the midst of or at risk for an infectious outbreak, added attention should be paid to the choice of geographic location that ensures security of the site, more controlled access, vector control, and which mitigates the environmental spread of contagion. Particularly, site selection should focus on effective and manageable clean water and sanitation, as well as possibly prevailing wind patterns, which may influence the spread of disease. If quarantine measures are in practice for the field hospital, the added burden of security may become paramount in deciding where to locate a facility.

The physical structure, organic supplies, and mobility of a field hospital are all characteristics that must be considered when planning for a facility’s deployment for surge bed capacity during a contagious outbreak. Not all types of deployable field hospital platforms are amenable to be configured for adequate infection control, both in terms of physical barriers and standard operating procedures (SOPs). Thoughtful and deliberate consideration of how a particular field hospital platform can accommodate such measures must be conducted and ideally exercised in contingency planning scenarios; if at all possible, well in advance of an actual event. One important physical attribute that should be addressed is whether the layout can be adapted to ensure patient isolation, for instance. SOPs for infection control that many clinical providers are familiar with in routine practice within fixed hospital or clinic facilities may not be readily translated to the field-hospital setting. In part, this may be due to the physical layout of the field hospital or it may relate to the inherent supplies of the field hospital under normal, noncontagious threat conditions. Most notably, more aggressive standards for personal protection may be required in the field-hospital setting under a contagious epidemic threat than are usually accounted for in supplying a field hospital under other disaster conditions. Additionally, certain higher levels of care including field surgery or intensive care unit (ICU) level cardiovascular and respiratory support may be deemed very high risk or yield very low reduction in patient mortality in the context of certain contagious pathogens and associated morbidities; and, therefore, the field hospital supplies routinely stocked to support these clinical activities may be deemed unnecessary as clinical care is focused on more basic supportive care. Such was the case in the setting of ETUs in 2014–2015 in West Africa[12].

Figure 25.1 Aerial view of the US public-health service Monrovia Medical Unit, 2015

The profile of the personnel employed to staff a field hospital requires equal scrutiny to that of the platform. It is not uncommon for field hospitals deployed to disaster situations to be more heavily weighted in terms of clinical personnel and materiel toward acute, emergent, and surgical care. Primary-care medicine is often adjunctive to the focus of care that is directed toward emergent lifesaving efforts. While that balance of clinical skills may be appropriate in disaster scenarios of a certain type (e.g., immediately post-earthquake), in the setting of a clinical and public-health concern mainly for infectious disease, clinical staffing of the field hospital ought to reflect predominantly primary care skills. Depending on the scale of the epidemic crisis and the availability of resources to address the clinical needs, the extent of medical and surgical care rendered may be limited to attempts to help the greatest numbers of patients to survive[13]. Selection of staffing for the field hospital should therefore appropriately balance clinical skill sets with the parameters for the delivery of care that have been defined. Generally, for a larger scale infectious outbreak, clinical care (and therefore the profile of the field hospital staffing) would be directed toward basic supportive care, ensuring adequate hemodynamic and respiratory support commensurate with bed capacity, patient volume, and available resources. Resource constraints and infection control measures may dictate limited, if any, ventilator support or renal replacement therapy, as cases in point. Nevertheless, expertise of clinical providers from certain specialty fields, such as infectious disease, intensive care, pediatrics, and obstetrics, may be value-added if the parameters for delivering care afforded more aggressive management strategies and/or the patient population served was expected to weigh toward children and pregnant women.

Additional focus on staffing of the field hospital in circumstances of an infectious-disease threat needs to be directed toward ensuring skills sets in infection control, preventive medicine, epidemiology, and environmental engineering. In addition, given the importance of early diagnosis of infection for certain pathogens in helping to determine isolation procedures and clinical management strategies for patients, more unique laboratory skills and resources may be required than is typical of most field-hospital deployments. Laboratorians skilled and resourced to diagnose pathogens and their differential counterparts can contribute greatly to all other aspects of patient regulation in the field-hospital setting under contagious threat. It may be necessary to ensure a significant proportion of staffing overall is exclusively focused on infection control, decontamination, safety, and preventive-medicine strategies for the field hospital; benefitting patients and providers equally. Epidemiologists and other public-health specialists may be valuable for the mission of the field hospital under such conditions to provide effective case definitions, tracking, and support contact tracing to relevant public-health agencies. In providing clinical care to Ebola patients in West Africa, extraordinary attention was paid to nonclinical staffing, as much as to those providing beside care directly to patients (Table 25.1).

Consistent with the staffing of a field hospital under any conditions, appropriate training of personnel is imperative for them to adequately function in the more austere conditions. Generically, there are many aspects of clinical care in the field-hospital setting that demand nuanced training in contrast to how professionals might otherwise be trained to deliver care in their normal work environments. Such nuanced training may become all the more important in the situation of a deployed field hospital responsive to a crisis with an epidemic contagious threat. Inherent in the planning for such field-hospital conditions is the need for appropriately focused training toward the biological threat, in terms of its epidemiology, its clinical presentation, and relevant clinical management protocols, and perhaps most importantly, its attendant risk of transmission and the management strategies for infection control within the field hospital. The psychological stress of working in an environment where there is a real risk of personnel acquiring disease must be addressed overtly when preparing staff for such a scenario. The requirement for such specific training was made clear in the Ebola outbreak of 2014–2015. It was readily apparent that very few responders were adequately prepared to safely and effectively deliver clinical care in tertiary care centers in developed countries, much less in the conditions in West Africa within field hospitals. An enormous effort was made to rapidly develop and deliver appropriate training in clinical care and infection prevention and control to ensure responders were available to function in field settings and to do so with as little risk as possible[14–16].

The nature and extent of clinical care delivered in a field-hospital setting varies tremendously with the scope and scale of the crisis or disaster confronted. As has been discussed, the inherent capabilities and capacities of a field hospital platform and its personnel are factors that define the limits of care that need be applied. However, in the context of a contagious pathogen impacting a community, and particularly impacting that community in a manner that exceeds the resources available to normally respond to clinical and public-health demands, the parameters for the delivery of clinical care may be greatly influenced by balancing the risk of transmission of disease with the impact of clinical interventions on morbidity and mortality. An infectious agent that is causing disease in a larger and larger number of patients, and one that has a high attack rate (degree of transmission from one person to another) with a mechanism of spread difficult to control, potentially places significant limitations on the manner in which care can be safely rendered in the field-hospital setting. The extreme example of a highly infectious, highly virulent, airborne-spread virus would put an enormous burden on a field hospital in terms of standards of infection control and the required material and personnel skills to safely care for patients. Even in the less severe example of a contagion that is spread via contact with bodily fluids, the burden on resources in a field-hospital setting can be extraordinary. No matter how grave the infectious risk is, planning for the delivery of care in the field hospital must take into consideration the appropriate level of personal protection and environmental controls. It is not clear from recent global experience or existing planning considerations that an adequate availability of resources exists to support a large-scale field hospital response for surge bed capacity in a global pandemic scenario[17].

The adequacy and timeliness of information in periods of crisis is critical to effective disaster medical assistance. The epidemiology of various types of disasters in different populations in different environments can and has been modeled[18]. For more static events leading to disaster, such as a bombing or earthquake, predictive modeling has demonstrated to have some benefit[19]. How predictive those models are to accurately plan for requirements for field hospitals in all scenarios is debatable, however. As was realized in the evolving Ebola epidemic in West Africa, predictions for the spread of epidemic disease and therefore assessments of the commensurate burden on clinical bed capacity are potentially more problematic. The accurate planning for and deployment of field hospitals to a particularly dynamic situation such as an evolving epidemic crisis is therefore dependent on real-time data and analytics. Medical and epidemiologic information should be sought early in planning for field hospital operations to best align the physical requirements of a facility as well as the requirements for personnel and training against the mission. A field hospital’s success will depend significantly on planning that addresses accurate information regarding the infectious agent, specifically its clinical and epidemiologic profile.

Equal to the need for accurate data up front in the planning for field-hospital operations in the face of a contagious outbreak is the need to plan for data collection within the facility. Beyond the value in improved clinical care for patients, accurate and complete data collection in the field-hospital setting can provide important health data to the larger public-health response during a crisis. Clinical and demographic data obtained from patients in the field hospital can be applied discretely and aggregated to help inform the broader public-health picture of an epidemic crisis and direct public-health interventions to control for the further spread of disease. In planning for a field-hospital engagement under such circumstances it behooves medical planners to develop systems of data collection which can easily be shared with public-health authorities. As well, such an approach of information sharing needs to be built into planning for training purposes for field hospital staff.

A final planning consideration for field hospitals in the context of an infectious outbreak is in appropriately managing information sharing with the public. Given the prominent role that strategic and risk communications play in public-health crises, information sharing regarding the spread of disease ought to be appropriately vetted and controlled. An accurate representation of the epidemiology and clinical aspects of the disease, which is evidenced-based, is necessary to minimize public distrust and uncertainty in such crises. Field-hospital planners must account for how information relating to their operations and their patients is integrated into the larger public-health-risk communications strategy.

Preparation

Rarely, if ever, in emergent disaster response situations will the planning cycle for the deployment of a field hospital to a particular scenario be fully realized before establishment of the facility is necessary. The issues on the ground more often define the timeliness of executing the mission of a field hospital than does the completeness of planning activities. Given this limitation, contingency plans need to be entertained well in advance of crises where field hospitals may be employed to help manage unique contagious threats. Failing such comprehensive advanced planning for varying field-hospital configurations and operating procedures, quick and deliberate preparation for operations must often be conducted in real time while finalizing elements of the planning for a given situation. In practice, this demands flexibility and innovative skills to further planning considerations along while actually laying out the physical platform of the field hospital and rehearsing SOPs, focused on the known clinical and infection control issues at hand.

In the context of infectious disease risks, including to the patient population served and the personnel rendering care in the field hospital, appropriate preparation of the facility and practiced operational procedures are imperative. The effectiveness of clinical-care practices to treat patients and preventive medicine strategies to mitigate the spread of contagious disease within the facility is directly correlated with the design of the field hospital and the procedures employed by staff[20]. While appropriate immunization status should be demanded of all field-hospital personnel under any conditions as a best preventive medicine practice, situations where there is risk of a contagious pathogen present additional impetus for targeted vaccination. When feasible, relative to the specific infectious threat, directed vaccination of staff should be sought. In the case of emerging biological threats, where fully validated vaccines may not be available, but a vaccine may exist that is under study, a unique sociopolitical and clinical/scientific set of considerations needs to be weighed to entertain the protection of those personnel, many of whom are volunteers.

The design of the field hospital, relative to infectious risks and clinical requirements for managing patients, will vary considerably with the nature of the pathogen, or pathogens, that are prevalent. Low-risk versus high-risk contact isolation necessitate different considerations for patient triage, segregation, and movement through the facility, as well as movement of staff. These considerations could directly impact the layout of the field hospital in profound ways. The selection of the type of platform to be used for the field hospital should be considered early on in planning given the limitations of certain facilities to adequately accommodate these requirements. The design of ETUs in West Africa in 2014–2015 is a demonstrative example of the importance of layout and patient and staff movement. In this example of extreme contact isolation, design was influenced in every conceivable way to minimize droplet spread of disease – unidirectional flow of patients and staff through the facility, segregation of suspect versus confirmed patients, placement of decontamination stations, distancing of beds, and complete separation of high-risk and low-risk zones are but a few examples of measures taken.

While there are subtleties that need to be addressed with many different types of contagious pathogens, one major discriminator in the design of a field hospital during a contagious threat is whether there is risk of airborne spread. Very few platforms exist for field-hospital deployment that can accommodate the limitations of a facility attempting to control for the airborne spread of a highly infectious contagion, particularly under exaggerated conditions with large numbers of patients necessitating significant bed capacity. There remain little data on the adequacy of physical or procedural barriers to minimizing airborne pathogen spread in the field hospital setting[21].

Beyond the choice of platform and the configuration of a facility to accommodate the physical barriers needed to manage infectious disease risk, the preparation of SOPs to control for disease spread while maximizing patient care demands equal or greater attention. Like advanced planning for the physical design of a field hospital under various contingency scenarios with infectious disease risk, advanced development of SOPs should be sought. SOPs for fixed medical treatment facilities under nonemergent or disaster conditions can be modified for the field hospital setting. Early planning that accounts for the potential limitations of a field hospital in more austere circumstances can help minimize the real-time preparations required once a field hospital is deployed. Nevertheless, any preplanned SOPs must be exercised in the setting of the deployed field hospital prior to receipt of a first patient, whenever possible. There will always be unforeseen limitations to the application of SOPs within a field hospital that are situation-dependent and that require modification of the SOPs to ensure good clinical care and safe infection control measures.

Just-in-time training of personnel will always be required in considering infectious disease risk in a field hospital setting. It is unlikely that any or all personnel deployed to support a field hospital will have the complete knowledge, skills, and abilities to address a given communicable disease scenario, including awareness of the type of platform being employed for the field hospital, the logistical limitations for the field hospital, the specific steps of the SOPs being applied, the characteristics of the pathogen(s) that are prevalent, the pathophysiology and epidemiology of the disease being addressed, or the cultural variations that are relevant to the population being served. All these issues need to be raised in the consciousness of personnel staffing a field hospital under such a contagious disease threat. This demands that a great deal of attention is paid, at the time of preparation of a facility, to innovative means of training and education. Much of the just-in-time training will need to be developed in a notional sense. However, whenever possible, additional real-world experience for personnel should be sought before executing the mission of the field hospital. This can be conducted with aligned partners in the crisis, if there are other actors conducting similar operations ahead of the mission at hand.

Medical record keeping, by whatever means, is always a necessity and often a challenge in the field hospital setting. However, in the context of a communicable disease outbreak, either as the primary or secondary issue in a crisis situation, accurate health records can also be vital to the larger public-health concerns. Patients with infectious disease who are clinically cared for in a field hospital represent part of the broader picture of the health-related event. Information that addresses how a patient acquired the disease, their clinical status, and response to therapy could inform public-health measures for contact tracing, control of further spread of disease, and future clinical management strategies for the care of other patients. Therefore, establishing an effective and efficient system of record keeping, and one that can be accessed by the public-health community, for the field hospital in the scenario of a contagious disease outbreak becomes essential.