Hospitals need specialized high-level isolation units to care for patients with highly contagious infectious diseases while protecting healthcare workers, other patients, and the wider public. Outbreaks involving pathogens such as Ebola have shown how quickly these threats can test hospital preparedness and expose weaknesses in infection-control systems.

In Spain, the Ebola epidemic that devastated West Africa between 2013 and 2016 became a major turning point in planning for such threats. The virus reached Spain in October 2014, when a nursing assistant became the first recorded case of local Ebola transmission outside Africa. That crisis exposed shortcomings in the system and underscored the urgent need for specialized facilities capable of delivering high-quality patient care while maintaining the highest possible level of protection for staff and society as a whole.

Today, Spain has a network of high-level isolation units distributed across the country and recognized as designated national referral centers within the public health system. These are not simply reinforced isolation rooms but complex, multidisciplinary, highly specialized facilities that can be activated within hours when a patient with a highly contagious infectious disease is identified.

When Units Are Activated

The range of conditions that may require the use of these units is broader than it might seem. Among the most significant are viral hemorrhagic fevers (such as Ebola, Marburg virus, Lassa fever, or Crimean-Congo hemorrhagic fever), severe respiratory conditions caused by pathogenic coronaviruses, poxvirus infections, biologic agents that could be used in acts of bioterrorism, and, on occasion, certain severe infections caused by other microorganisms. All of these diseases share certain characteristics: high case fatality rates, the potential for transmission to healthcare workers caring for patients, and the need for care measures involving a very high level of containment.

Crimean-Congo hemorrhagic fever deserves special mention as the first cases of local transmission were recorded in Spain in 2016, showing that these threats are not confined to distant countries. Currently, globalization — with increased international mobility — and climate change, which is expanding the range of vectors such as ticks, are creating conditions in which pathogens previously endemic to remote regions can appear in new settings through imported cases, repatriations, or even local transmission.

Unit Design and Layout

Entering one of these units requires passing through a carefully designed sequence of spaces. The architecture is not an aesthetic whim but a fundamental tool for infection control.

The design includes an access area with strict tracking of personnel entering and exiting, changing rooms with showers, and a specially designated area for putting on personal protective equipment (PPE), ideally equipped with a video camera and a full-length mirror so that healthcare professionals can verify that no area is left exposed. Before reaching the patient’s room, there is an airlock — an intermediate transition zone that is critical for preventing indoor air from escaping to the outside.

The room itself must be at least 9 m² and is equipped with audiovisual communication systems connecting to the nursing station, an intercom system, a video camera, and an accessible bathroom. One of the most important technical features is the air-handling system: The room maintains negative air pressure relative to adjacent areas, which prevents indoor air from escaping into the rest of the hospital. The system performs at least 12 air changes per hour and features four redundant high-efficiency particulate air filters that trap microorganisms before the air is expelled outdoors. All materials in the room are resistant to hydrogen peroxide, a substance used for disinfection.

The units also include an on-site biosafety laboratory of at least biosafety level 2, with a biosafety level 3 cabinet, which allows certain samples to be processed without having to transfer them to other areas of the hospital, thereby avoiding the associated risks. For biosafety level 4 pathogens, such as the Ebola or Marburg viruses, cultures and more complex procedures must be referred to specialized reference laboratories.

Finally, the design also includes rest areas for staff, storage areas for consumables and PPE, medication storage areas, equipment disinfection areas, and a disinfection system using atomized hydrogen peroxide.

Protective Equipment

For an outside observer, seeing a healthcare professional dressed in full personal protective equipment can be striking. For the person wearing it, working for hours under these conditions is a physically demanding experience. For both, the proper use of this equipment can literally be a matter of life and death.

In the context of these units, the standard protective gear used in a conventional hospital is insufficient. While gloves, a disposable gown, a surgical mask, and eye protection are adequate for the routine care of many infectious patients, in high-level units, protection must be comprehensive and leave no area of skin or mucous membranes exposed.

In Spain, the most advanced PPE used for infectious patients, particularly where airborne transmission is a concern, includes high-filtration efficiency respirators (FFP2 for general care and FFP3 for aerosol-generating procedures such as intubation, bronchoscopy, or suctioning of secretions), a long-sleeved waterproof gown, double gloves, full-face eye protection, and shoe covers. In high-level units, all these items are put on and removed in accordance with standard operating procedures that specify the exact order of donning and, above all, doffing.

Removing PPE is, in fact, the moment of greatest risk for contamination. During this process, the exterior of the equipment is contaminated, and any error can transfer the infectious agent to the healthcare worker’s skin or mucous membranes. For this reason, units require that this procedure be performed according to a strict step-by-step protocol and under the direct supervision of another trained healthcare professional. It is also recommended that the PPE removal area be equipped with a full-length mirror and, if possible, video cameras that allow an external supervisor to detect any procedural errors.

The order of removal, according to international guidance applied within the Spanish system, generally begins with the outer gloves, followed by eye protection, the gown, and shoe covers, and ends with the mask, which is the last item to be removed precisely because it protects the most direct entry point into the body. Hand hygiene is performed between each step because it is considered the most effective preventive measure in the entire infection-control arsenal.

Staffing and Training

A unit of this nature cannot function without a properly sized and continuously trained team. In the Spanish model, the core team includes, at a minimum, a care coordinator responsible for managing the unit, 5 physicians specializing in infectious diseases, 5 intensivists, 20 nurses, and 12 nursing assistants if the unit has a single bed; these numbers increase to 30 nurses and 18 nursing assistants in two-bed units. In addition to this core team, there are security, cleaning, and waste-management staff specifically trained for this context.

But the mere existence of the team is not enough: Ongoing training is essential. Each assigned professional must participate in at least three annual practical exercises on putting on and removing protective equipment, as well as in one full-scale simulation of the unit’s activation per year, which includes receiving a simulated patient with a high-risk infectious disease. These exercises are supervised by the occupational safety and health department, and the results are recorded individually.

Training is not just technical. Working under high-stress conditions — with protective gear that limits vision, verbal communication, and manual dexterity — and taking on the responsibility of caring for a patient with a potentially life-threatening illness also requires training in teamwork and emotional management under pressure.

Waste and Disinfection

Everything that leaves the room of a patient admitted to one of these units is considered potentially hazardous. Waste is classified and managed as high-risk biological waste under current legislation, with specific routes within the hospital until it reaches its final collection point. Disposable materials used by the patient, including cleaning materials, are always treated under this category. The containers are airtight, and any spill of biological fluids triggers a specific containment protocol.

Terminal disinfection of the room, once the patient is discharged or transferred, is performed by hydrogen peroxide fogging, a process that ensures the elimination of infectious agents on all surfaces, including corners that are difficult to reach by manual cleaning.

A Network on Alert

High-level isolation units are not operating at full capacity all the time. During periods of inactivity, the professionals assigned to them carry out their regular duties in their respective departments, such as infectious diseases, intensive care, pediatrics, or nursing. The unit, however, remains ready to be activated within 4-6 hours of the decision to admit a patient.

This rapid response capability depends on continuous coordination between regional public health authorities and Spain’s Ministry of Health and is integrated into the national epidemiologic alert system. Ultimately, these units represent the first line of hospital response to the most severe infectious threats, and their existence is a safeguard both for the patients who need them and for the wider public.

This story was translated from Univadis Spain, part of the Medscape Professional network.