Infectious disease outbreak response — PPE, isolation, AGPs

Definition / Overview

An infectious disease outbreak in the ED context is defined as a cluster of cases exceeding the expected endemic rate, posing a risk of healthcare-associated transmission to staff, patients, and visitors. The ED is uniquely vulnerable: undifferentiated presentations, crowding, high patient turnover, and procedural activity all amplify transmission risk.

The ED response requires simultaneous activation of clinical, organisational, and public health functions. Core pillars are:

• Triage screening to identify and separate potentially infectious patients at the earliest point of contact
• Source isolation and cohorting to prevent cross-transmission within the department
• Appropriate PPE selection and technique matched to the transmission route of the suspected or confirmed pathogen
• Control of aerosol-generating procedures (AGPs)
• Staff health surveillance and occupational health linkage
• Infection control liaison and public health notification

Transmission Routes and Precaution Tiers

Understanding the transmission route determines the PPE level required. The three tiers build on a universal base of standard precautions (hand hygiene, gloves, gown and eye or mucous membrane protection when splash is possible).

Bioterrorism caveat: For an unknown biological hazard in a deliberate release event, treat as requiring standard, contact, and airborne precautions simultaneously until the pathogen and its transmission profile are established.

Triage Screening

Principles

• Screening must occur at the earliest point of patient contact, ideally before or immediately on entry to the building, not at the cubicle
• During a recognised outbreak, a dedicated screening station positioned at the external entry is preferable, allowing diversion before the patient enters the main department
• The screening tool should identify:
  • Fever ($\geq 38^\circ\text{C}$)
  • Cough, dyspnoea, rash, or other syndrome-specific symptoms
  • Relevant exposure history (geographic, occupational, household contacts)

Immediate actions at triage

1. Apply a surgical mask to any patient meeting the illness definition; direct them to hand hygiene resources before further contact with the waiting area
2. Seat the patient at least 1 m from other patients or, preferably, a separate waiting zone
3. Fast-track to a single isolation room with the door closed and appropriate signage indicating the required precaution level
4. Minimise the number of staff who enter; assign a dedicated nurse and treating clinician
5. Document the time of identification and time of isolation for outbreak reporting purposes

Special populations at triage

• Pregnant patients require extra caution during examination, particularly if delivery is anticipated; use elbow-length gloves and position staff to the side rather than directly in front during any delivery
• Patients who are immunocompromised, elderly, or have haematological malignancy should not be cohorted with infectious patients and require prioritised access to single rooms

Source Isolation and Cohorting

Single-room isolation

• The first-line response for any patient meeting the case definition is placement in a single enclosed room with en suite facilities
• For airborne pathogens: the room must have negative-pressure ventilation with 6-12 air changes per hour and discharge of room air to the outdoors or through high-efficiency filtration; an anteroom with donning and doffing facilities is ideal
• For droplet pathogens: a standard single room with the door kept closed is required; special air handling is not mandated but spatial separation of $\geq 1\,\text{m}$ from all other patients must be maintained
• For contact pathogens: a single room is preferred; if unavailable, maintain distinct zones and dedicate all equipment to that patient

Cohorting

When single rooms are exhausted:

• Cohort confirmed cases with the same pathogen in a shared space, separated from patients with other diagnoses
• Probable or suspect cases should be kept in a separate zone from confirmed cases wherever space permits, to avoid exposing unconfirmed patients to a definite pathogen
• Do not cohort immunocompromised or high-risk patients with infectious patients

Physical ED layout considerations

• The isolation room should be positioned away from main thoroughfares to avoid inadvertent cross-traffic
• A decontamination area accessible directly from the ambulance bay, with a floor drain and contamination water trap, enables management of patients contaminated with hazardous substances without compromising the main department
• During surge, consider repurposing ED short-stay or adjacent clinic space as a dedicated fever area

PPE: Selection, Donning, and Doffing

PPE for each precaution level

Donning sequence (standardised)

1. Perform hand hygiene
2. Don gown: secure at neck and waist
3. Don respirator or surgical mask: perform fit-check for N95 (positive and negative pressure seal test)
4. Don eye protection (goggles or face shield)
5. Don gloves: extend cuffs over gown wrists

Doffing sequence (highest contamination risk step)

Doffing carries greater risk of self-contamination than donning. A buddy system is mandatory: a trained observer supervises every doff and calls out any breach.

1. Remove gloves: peel away without touching outer surface; perform hand hygiene
2. Remove gown: roll outward away from body; perform hand hygiene
3. Remove eye protection: handle by the strap or arms only; perform hand hygiene
4. Remove mask or respirator: handle by straps only, bring forward away from face; perform hand hygiene
5. Perform final hand hygiene

Key rules:

• Use the same standardised sequence each time; use a written or laminated SOP at the doffing station
• Clean gloves with 0.5% hypochlorite solution between patients; dry before patient contact; 0.05% hypochlorite is used for hand hygiene in Ebola-level situations where alcohol hand rub is contraindicated by local protocol
• Report all PPE breaches immediately to the occupational health lead; document in the incident reporting system
• Needlestick or mucous membrane exposure: cease work immediately, perform first aid, and seek urgent expert advice regarding post-exposure prophylaxis from the treating hospital's occupational health team, the relevant state health department, or an infectious diseases physician; the Australian Poisons Information Centre (13 11 26) can provide supplementary guidance on chemical or toxin exposures

Aerosol-Generating Procedures

Definition and significance

AGPs produce aerosols of particles $< 5\,\mu\text{m}$ that remain suspended in air well beyond the 1-2 m droplet zone. In pathogens where baseline precautions are droplet-level, AGPs mandate upgrading to full airborne precautions regardless of baseline transmission category.

Recognised AGPs in the ED

• Endotracheal intubation and laryngoscopy (the highest-risk AGP)
• Bag-mask ventilation
• Non-invasive ventilation (CPAP, BiPAP)
• Nebulised medication administration
• Bronchoscopy
• High-flow nasal oxygen
• Open suctioning
• Cardiopulmonary resuscitation
• Chest physiotherapy

AGP management principles

1. Limit the number of personnel in the room to the minimum required to safely perform the procedure
2. Upgrade PPE to full airborne level: fitted N95 or higher, gown, double gloves, full face shield
3. Perform AGPs in the negative-pressure isolation room whenever possible
4. If no negative-pressure room is available: use a single room with the door closed; following nebuliser use, that room must not be occupied by a new patient for at least 60 minutes (minimum clearance time for aerosolised particles in a standard single room at normal pressure)
5. For intubation: use video laryngoscopy to increase distance from the airway; perform RSI to minimise coughing (ketamine $1.5\,\text{mg/kg}$ IV + rocuronium $1.2\,\text{mg/kg}$ IV is the standard RSI sequence in the ED); have airway equipment immediately ready, minimise pre-oxygenation with BVM if possible by using a tightly fitting mask or high-flow nasal oxygen, and apply a viral filter to the circuit
6. Prefer pMDI with spacer over nebuliser for bronchodilator delivery where clinically equivalent (e.g. salbutamol 8 puffs via spacer every 20 minutes); reserve nebulisation for patients too unwell to use a spacer, with full airborne precautions applied

Negative-Pressure Rooms

A compliant airborne infection isolation room must have:

• Monitored negative pressure relative to the surrounding corridor (typically $-2.5\,\text{Pa}$ or greater differential)
• 6-12 air changes per hour
• Exhaust air discharged directly to the outdoors or passed through high-efficiency particulate air (HEPA) filtration before recirculation
• A closed door at all times; an anteroom is ideal
• Visual pressure monitoring (usually a pressure gauge or smoke-test visible from outside the room)

The number of negative-pressure rooms in most Australian EDs is limited: typically one to two. Prioritisation during surge must be explicit:

• Pulmonary tuberculosis (mandatory)
• Measles, varicella in infectious period
• Any suspected novel or high-consequence respiratory pathogen
• Any patient undergoing an AGP if the above rooms are occupied

When demand exceeds supply, escalate to the hospital infection control team and hospital executive for access to inpatient negative-pressure capacity.

Staff Health Monitoring

During an outbreak

• Establish a staff symptom register: all ED staff should self-monitor twice daily for fever ($\geq 38^\circ\text{C}$) and respiratory or other syndrome-specific symptoms for the relevant incubation period after last potential exposure
• Any contact without adequate PPE constitutes a high-risk exposure: the individual should be stood down from clinical duties and referred immediately to occupational health
• Contacts with adequate PPE are low-risk exposures: surveillance only, with low threshold to stand down if symptoms develop
• Contacts who develop fever or meet the case definition during the surveillance window must be isolated immediately and assessed as a potential case

Vaccination and prophylaxis

• Confirm that all ED staff have current influenza vaccination
• For specific outbreaks (e.g. measles, hepatitis B, meningococcal disease), offer post-exposure prophylaxis or vaccination according to current Australian Immunisation Handbook recommendations and state health department guidance
• Maintain a record of staff vaccination status as part of occupational health preparedness

Infection Control Liaison and Public Health Notification

Internal liaison

• Notify the hospital infection control team at the earliest suspicion of an outbreak; they provide expertise on case definitions, PPE appropriateness, environmental cleaning, and laboratory specimen handling
• The occupational health unit manages staff exposures, PPE breaches, and return-to-work decisions
• The hospital laboratory must be alerted before specimens from high-consequence pathogen cases are submitted; some specimens require transport to specialised reference laboratories (e.g. Ebola serology to a state reference laboratory)
• ED medical leadership should escalate to the hospital executive early to activate surge and business continuity plans

External notification

• State and territory public health units must be notified immediately for all notifiable conditions; the list is jurisdiction-specific and maintained by each state health department
• For conditions with potential for international spread, the relevant state health department will notify the Commonwealth Department of Health, which in turn has obligations to the World Health Organization under International Health Regulations
• ED clinicians are not expected to manage the full public health response but must know their notification responsibility and act without delay
• Contact tracing for identified cases (including staff exposures) is coordinated by the public health unit; the ED should provide accurate timelines and exposure lists

Environmental cleaning

• All surfaces in the isolation room and any areas the patient transited should be cleaned with an appropriate disinfectant agent as directed by the infection control team (commonly hypochlorite-based solutions for VHF-class pathogens)
• Equipment must be either dedicated to the patient and not shared, or decontaminated between patients with a validated agent; never share equipment between patients when sharing can be avoided

Complications and Special Considerations

Staff wellbeing

Outbreaks generate significant psychological stress from fear of personal infection and concern about infecting household contacts. ED leadership must:

• Provide clear, timely communication about the pathogen, transmission risk, and PPE adequacy
• Arrange access to employee assistance programs
• Rotate staff away from high-exposure areas to limit fatigue and maintain capability

Candidate errors to avoid in the exam

• Failing to specify that nebulised medications require airborne precautions, not just droplet precautions
• Omitting the 60-minute room clearance period after nebuliser use in a non-negative-pressure room
• Describing doffing without nominating the buddy supervision requirement
• Not mentioning public health notification as a mandatory, time-critical step
• Selecting contact-only precautions for pneumonic plague (droplet required) or droplet-only for smallpox (combined airborne + contact required)
• Failing to specify video laryngoscopy and RSI as the preferred intubation approach for high-consequence respiratory pathogens

Disposition and System Considerations

Sources

• ACEM policy documents
• Therapeutic Guidelines (eTG)