Validation of personal protective equipment ensembles, incorporating powered air-purifying respirators protected from contamination, for the care of patients with high-consequence infectious diseases.

BACKGROUND: The UK High-Consequence Infectious Diseases (HCID) Network of high-level isolation units provides care for patients with contact- or airborne-transmissible highly infectious and highly dangerous diseases. In most HCID units, the healthcare workers (HCWs) wear personal protective equipment (PPE) ensembles incorporating a powered air-purifying respirator (PAPR) for head and respiratory protection. Some PAPRs have components worn outside/over other PPE, necessitating decontamination of re-usable elements. Two alternative PAPRs, with all re-usable elements worn under PPE, were trialled in this study. AIM: To undertake scenario-based testing of PAPRs and PPE to determine usability, comfort and ability to remove contaminated PPE without personal cross-contamination. METHODS: Trained healthcare volunteers (N=20) wearing PAPR/PPE ensembles were sprayed with ultraviolet fluorescent markers. They undertook exercises to mimic patient care, and subsequently, after doffing the contaminated PPE following an established protocol, any personal cross-contamination was visualized under ultraviolet light. Participants also completed a questionnaire to gauge how comfortable they found the PPE. FINDINGS AND CONCLUSIONS: The ensembles were tested under extreme 'worst case scenario' conditions, augmented by physical and manual dexterity tests. Participating volunteers considered the exercise to be beneficial in terms of training and PPE evaluation. Data obtained, including feedback from questionnaires and doffing buddy observations, supported evidence-based decisions on the PAPR/PPE ensemble to be adopted by the HCID Network. One cross-contamination event was recorded in the ensemble chosen; this could be attributed to doffing error, and could therefore be eliminated with further practice.

Potential distribution of viable norovirus after simulated vomiting.

BACKGROUND: Vomiting is one way in which the body rids itself of harmful gastric contents rapidly. Whilst this process is generally beneficial for the emetic individual, it can pose significant infection control issues if they are infected with a highly communicable pathogen such as norovirus. It is not known how far norovirus could spread through vomiting while remaining viable, particularly in far-reaching droplets and splashes that might be missed during cleaning. AIM: To identify the potential level of dissemination of viable norovirus after simulated vomiting. METHODS: This study used a system called 'Vomiting Larry' to simulate vomiting with infection medium containing the norovirus surrogate feline calicivirus (FCV) as a worst-case scenario for distribution and survival of viruses after simulated vomiting. Air and floor samples were taken after simulated vomiting, and analysed for viable virus via plaque assay. Analysis of covariance investigated differences in FCV concentration by sample volume and location. FINDINGS: Whilst viable virus was not isolated from any air samples taken after simulated vomiting, FCV concentrations of ≥10 plaque-forming units/mL were recovered from almost all samples taken from the floor (88/90). These included small droplets of fluid that travelled 3 m away from the vomiting system. There was evidence that FCV concentration depended on both sample volume and location. CONCLUSION: This study suggests that norovirus can survive being ejected even within small far-reaching droplets at concentrations capable of eliciting infection. Such droplets could easily go unnoticed and be overlooked during cleaning, adding to the challenge of controlling norovirus outbreaks.

Guidance on the use of respiratory and facial protection equipment.

Infectious micro-organisms may be transmitted by a variety of routes, and some may be spread by more than one route. Respiratory and facial protection is required for those organisms that are usually transmitted via the droplet/airborne route, or when airborne particles have been artificially created, such as during 'aerosol-generating procedures'. A range of personal protective equipment that provides different degrees of facial and respiratory protection is available. It is apparent from the recent experiences with severe acute respiratory syndrome and pandemic (H1N1) 2009 influenza that healthcare workers may have difficulty in choosing the correct type of facial and respiratory protection in any given clinical situation. To address this issue, the Scientific Development Committee of the Healthcare Infection Society established a short-life working group to develop guidance. The guidance is based upon a review of the literature, which is published separately, and expert consensus.

Effectiveness of surgical masks against influenza bioaerosols.

BACKGROUND: Most surgical masks are not certified for use as respiratory protective devices (RPDs). In the event of an influenza pandemic, logistical and practical implications such as storage and fit testing will restrict the use of RPDs to certain high-risk procedures that are likely to generate large amounts of infectious bioaerosols. Studies have shown that in such circumstances increased numbers of surgical masks are worn, but the protection afforded to the wearer by a surgical mask against infectious aerosols is not well understood. AIM: To develop and apply a method for assessing the protection afforded by surgical masks against a bioaerosol challenge. METHODS: A dummy test head attached to a breathing simulator was used to test the performance of surgical masks against a viral challenge. Several designs of surgical masks commonly used in the UK healthcare sector were evaluated by measuring levels of inert particles and live aerosolised influenza virus in the air, from in front of and behind each mask. FINDINGS: Live influenza virus was measurable from the air behind all surgical masks tested. The data indicate that a surgical mask will reduce exposure to aerosolised infectious influenza virus; reductions ranged from 1.1- to 55-fold (average 6-fold), depending on the design of the mask. CONCLUSION: We describe a workable method to evaluate the protective efficacy of surgical masks and RPDs against a relevant aerosolised biological challenge. The results demonstrated limitations of surgical masks in this context, although they are to some extent protective.