Correction to: Use of medical face masks versus particulate respirators as a component of personal protective equipment for health care workers in the context of the COVID-19 pandemic.

An amendment to this paper has been published and can be accessed via the original article.

Use of medical face masks versus particulate respirators as a component of personal protective equipment for health care workers in the context of the COVID-19 pandemic.

Currently available evidence supports that the predominant route of human-to-human transmission of the SARS-CoV-2 is through respiratory droplets and/or contact routes. The report by the World Health Organization (WHO) Joint Mission on Coronavirus Disease 2019 (COVID-19) in China supports person-to-person droplet and fomite transmission during close unprotected contact with the vast majority of the investigated infection clusters occurring within families, with a household secondary attack rate varying between 3 and 10%, a finding that is not consistent with airborne transmission. The reproduction number (R0) for the SARS-CoV-2 is estimated to be between 2.2-2.7, compatible with other respiratory viruses associated with a droplet/contact mode of transmission and very different than an airborne virus like measles with a R0 widely cited to be between 12 and 18. Based on the scientific evidence accumulated to date, our view is that SARS-CoV-2 is not spread by the airborne route  to  any significant extent and the use of particulate respirators offers no advantage over medical masks as a component of personal protective equipment for the routine care of patients with COVID-19 in the health care setting. Moreover, prolonged use of particulate respirators may result in unintended harms. In conjunction with appropriate hand hygiene, personal protective equipment (PPE) used by health care workers caring for patients with COVID-19 must be used with attention to detail and precision of execution to prevent lapses in adherence and active failures in the donning and doffing of the PPE.

Airborne transmission and precautions: facts and myths.

Airborne transmission occurs only when infectious particles of <5 µm, known as aerosols, are propelled into the air. The prevention of such transmission is expensive, requiring N95 respirators and negative pressure isolation rooms. This lecture first discussed whether respiratory viral infections are airborne with reference to published reviews of studies before 2008, comparative trials of surgical masks and N95 respirators, and relevant new experimental studies. However, the most recent experimental study, using naturally infected influenza volunteers as the source, showed negative results from all the manikins that were exposed. Modelling studies by ventilation engineers were then summarized to explain why these results were not unexpected. Second, the systematic review commissioned by the World Health Organization on what constituted aerosol-generating procedures was summarized. From the available evidence, endotracheal intubation either by itself or combined with other procedures (e.g. cardiopulmonary resuscitation or bronchoscopy) was consistently associated with increased risk of transmission by the generation of aerosols.

Debate on MERS-CoV respiratory precautions: surgical mask or N95 respirators?

Since the emergence of Middle East respiratory syndrome coronavirus (MERS-CoV) in mid-2012, there has been controversy over the respiratory precaution recommendations in different guidelines from various international bodies. Our understanding of MERS-CoV is still evolving. Current recommendations on infection control practices are heavily influenced by the lessons learnt from severe acute respiratory syndrome. A debate on respiratory precautions for MERS-CoV was organised by Infection Control Association (Singapore) and the Society of Infectious Disease (Singapore). We herein discuss and present the evidence for surgical masks for the protection of healthcare workers from MERS-CoV.

Infection prevention and control measures for acute respiratory infections in healthcare settings: an update.

Viruses account for the majority of the acute respiratory tract infections (ARIs) globally with a mortality exceeding 4 million deaths per year. The most commonly encountered viruses, in order of frequency, include influenza, respiratory syncytial virus, parainfluenza and adenovirus. Current evidence suggests that the major mode of transmission of ARls is through large droplets, but transmission through contact (including hand contamination with subsequent self-inoculation) and infectious respiratory aerosols of various sizes and at short range (coined as "opportunistic" airborne transmission) may also occur for some pathogens. Opportunistic airborne transmission may occur when conducting highrisk aerosol generating procedures and airborne precautions will be required in this setting. General infection control measures effective for all respiratory viral infections are reviewed and followed by discussion on some of the common viruses, including severe acute respiratory syndrome (SARS) coronavirus and the recently discovered novel coronavirus.

Infection prevention and control measures for acute respiratory infections in healthcare settings: an update

Viruses account for the majority of the acute respiratory tract infections [ARIs] globally with a mortality exceeding 4 million deaths per year. The most commonly encountered viruses, in order of frequency, include influenza, respiratory syncytial virus, parainfluenza and adenovirus. Current evidence suggests that the major mode of transmission of ARIs is through large droplets, but transmission through contact [including hand contamination with subsequent selfinoculation] and infectious respiratory aerosols of various sizes and at short range [coined as [opportunistic] airborne transmission] may also occur for some pathogens. Opportunistic airborne transmission may occur when conducting highrisk aerosol generating procedures and airborne precautions will be required in this setting. General infection control measures effective for all respiratory viral infections are reviewed and followed by discussion on some of the common viruses, including severe acute respiratory syndrome [SARS] coronavirus and the recently discovered novel coronavirus

Journey of a Hong Kong public teaching hospital in preparation of hospital accreditation.

Hospital accreditation is a new concept for Hong Kong Hospital Authority hospitals. Queen Mary Hospital has been engaged as one of the hospitals in a territory-wide Pilot Scheme of Hospital Accreditation. In preparation for accreditation, Queen Mary Hospital has undergone the process of self-assessment, staff engagement, and service improvements which all require well-planned strategies to achieve successful outcomes. In this article, we highlight the journey of preparation and the staff engagement exercise we conducted to attain full accreditation. We also highlight the obstacles, conundrums, and pitfalls we encountered, along with successful overcoming strategies and countermeasures we adopted, and quandaries to be avoided. Throughout the preparation, the hospital's senior executives insisted that achieving hospital accreditation was not the main focus, but rather an emphasis on how the Pilot Scheme would bring about organisational transformations in our culture, and thus foster quality, safety, effectiveness, and reliability of services. We hope our experience can provide a reference and be of value to other hospitals that will go through the journey in the future.

Seroprevalence of antibody to pandemic influenza A (H1N1) 2009 among healthcare workers after the first wave in Hong Kong.

During the first wave of an influenza pandemic prior to the availability of an effective vaccine, healthcare workers (HCWs) may be at particular risk of infection with the novel influenza strain. We conducted a cross-sectional study of the prevalence of antibody to pandemic influenza A (H1N1) 2009 (pH1N1) among HCWs in Hong Kong in February-March 2010 following the first pandemic wave. Sera collected from HCWs were tested for antibody to pH1N1 influenza virus by viral neutralisation (VN). We assessed factors associated with higher antibody titres, and we compared antibody titres in HCWs with those in a separate community study. In total we enrolled 703 HCWs. Among 599 HCWs who did not report receipt of pH1N1 vaccine, 12% had antibody titre ≥1:40 by VN. There were no significant differences in the age-specific proportions of unvaccinated HCWs with antibody titre ≥1:40 compared with the general community following the first wave of pH1N1. Under good adherence to infection control guidelines, potential occupational exposures in the hospital setting did not appear to be associated with any substantial excess risk of pH1N1 infection in HCWs. Most HCWs had low antibody titres following the first pandemic wave.

The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus.

The main route of transmission of SARS CoV infection is presumed to be respiratory droplets. However the virus is also detectable in other body fluids and excreta. The stability of the virus at different temperatures and relative humidity on smooth surfaces were studied. The dried virus on smooth surfaces retained its viability for over 5 days at temperatures of 22-25°C and relative humidity of 40-50%, that is, typical air-conditioned environments. However, virus viability was rapidly lost (>3 log(10)) at higher temperatures and higher relative humidity (e.g., 38°C, and relative humidity of >95%). The better stability of SARS coronavirus at low temperature and low humidity environment may facilitate its transmission in community in subtropical area (such as Hong Kong) during the spring and in air-conditioned environments. It may also explain why some Asian countries in tropical area (such as Malaysia, Indonesia or Thailand) with high temperature and high relative humidity environment did not have major community outbreaks of SARS.

Educating healthcare workers to optimal hand hygiene practices: addressing the need.

The education of healthcare workers is essential to improve practices and is an integral part of hand hygiene promotional strategies. According to the evidence reviewed here, healthcare worker education has a positive impact on improving hand hygiene and reducing healthcare-associated infection. Detailed practical guidance on steps for the organization of education programmes in healthcare facilities and teaching-learning strategies are provided using the World Health Organization (WHO) Guidelines for Hand Hygiene in Health Care as the basis for recommendations. Several key elements for a successful educational programme are also identified. A particular emphasis is placed on concepts included in the tools developed by WHO for education, monitoring and performance feedback.

Epidemiology and clonality of multidrug-resistant Acinetobacter baumannii from a healthcare region in Hong Kong.

We assessed the risk factors and molecular epidemiology of multidrug-resistant Acinetobacter baumannii (MDR-AB) in Hong Kong. The patients were treated in five hospitals in a healthcare region during 2005-2006. We performed genomic identification by amplified rRNA gene restriction analysis (ARDRA) and investigated the existence of metallo-beta-lactamases and the clonality of representative MDR-AB strains by phenotypic and molecular methods. Forty-five subjects with MDR-AB were compared with 135 controls (patients with no MDR-AB). In the logistic regression, chronic wound (odds ratio: 29.5, 95% confidence interval: 8.1-107.2; P<0.001) was the only factor independently associated with MDR-AB colonisation or infection. ARDRA identified all 45 MDR-AB as genomic species 2TU. Pulsed-field gel electrophoresis clustered all except two isolates into two clonal types, designated HKU1 and HKU2 with 24 and 19 isolates, respectively. The main features of HKU1 strains were ST26, adeB type XII, positivity for bla(OxA-23-like) and bla(OxA-51-like) genes and high level resistance to carbapenems. Most HKU1 strains retained susceptibility to gentamicin, cotrimoxazole and minocycline. By contrast, HKU2 strains exhibited ST22, adeB type II, and were usually positive only for the bla(OxA-51-like) gene and resistant to gentamicin, cotrimoxazole and minocycline. Both clones were found to have disseminated widely. In conclusion, clonal expansion is playing major roles in the increase of MDR-AB in these hospitals in Hong Kong. The findings highlight the need to enhance infection control measures.

Natural ventilation for reducing airborne infection in hospitals.

High ventilation rate is shown to be effective for reducing cross-infection risk of airborne diseases in hospitals and isolation rooms. Natural ventilation can deliver much higher ventilation rate than mechanical ventilation in an energy-efficient manner. This paper reports a field measurement of naturally ventilated hospital wards in Hong Kong and presents a possibility of using natural ventilation for infection control in hospital wards. Our measurements showed that natural ventilation could achieve high ventilation rates especially when both the windows and the doors were open in a ward. The highest ventilation rate recorded in our study was 69.0 ACH. The airflow pattern and the airflow direction were found to be unstable in some measurements with large openings. Mechanical fans were installed in a ward window to create a negative pressure difference. Measurements showed that the negative pressure difference was negligible with large openings but the overall airflow was controlled in the expected direction. When all the openings were closed and the exhaust fans were turned on, a reasonable negative pressure was created although the air temperature was uncontrolled. The high ventilation rate provided by natural ventilation can reduce cross-infection of airborne diseases, and thus it is recommended for consideration of use in appropriate hospital wards for infection control. Our results also demonstrated a possibility of converting an existing ward using natural ventilation to a temporary isolation room through installing mechanical exhaust fans.

Antimicrobial stewardship program directed at broad-spectrum intravenous antibiotics prescription in a tertiary hospital.

The antimicrobial stewardship program (ASP) is a major strategy to combat antimicrobial resistance and to limit its expenditure. We have improved on our existing ASP to implement a sustainable and cost-effective two-stage immediate concurrent feedback (ICF) model, in which the antimicrobial prescription is audited by two part-time infection control nurses at the first stage, followed by "physician ICF" at the second stage. In January 2005, an ASP focused on broad-spectrum intravenous antibiotics was implemented. All in-patients, except from the intensive care, bone marrow transplantation, liver transplantation, pediatric, and private units, being treated with broad-spectrum intravenous antibiotics were included. The compliance to ICF and "physician ICF", antibiotics usage density measured by expenditure and defined daily doses (DDD) were recorded and analyzed before and after the ASP. The overall conformance rate to antibiotic prescription guidelines was 79.4%, while the conformance to ICF was 83.8%. Antibiotics consumption reduced from 73.06 (baseline, year 2004) to 64.01 (year 2007) per 1,000 patient bed-day-occupancy. Our model can be easily applied even in the clinical setting of limited resources.

Nurses and physicians' perceptions of the importance and impact of healthcare-associated infections and hand hygiene: a multi-center exploratory study in Hong Kong.

BACKGROUND: Hand hygiene promotion for patient safety is a challenge worldwide, and local data are critical to tailor strategies to the setting. METHODS: This is a cross-sectional study of nurses and physicians providing direct patient care in four hospitals in Hong Kong using an anonymous questionnaire survey. Cognitive factors related to hand hygiene and the perception of effective interventions promoting hand hygiene were assessed. RESULTS: The overall response rate was 59.3%. Among respondents, 70% of the nurses and 49% of the physicians perceived that over 15% of patients would suffer from healthcare-associated infections. A total of 79% of the nurses and 68% of the physicians believed that more than 5% of patients would die as a result of healthcare-associated infection. A total of 60% of the nurses and 46% of the physicians acknowledged that over 75% of healthcare-associated infections could be prevented by optimal hand hygiene practices, although 36% of the nurses and 23% of the physicians claimed that six to ten hand cleansing times per hour would be necessary. Bivariate analysis showed significant differences between professionals in self-reported performance. A multivariate regression model revealed that perceived behavioral control and subjective norms were the most important factors associated with the nurses and physicians' self-reported hand hygiene performance. However when gender was taken into account among professionals, subjective norms was the only consistent one. CONCLUSION: These results could be used as a tool to create goal-specific strategies for motivating hand hygiene amongst nurses and physicians in Hong Kong, with appropriate promotional interventions delivered to the different professional groups and specialties.

Use of antibody avidity assays for diagnosis of severe acute respiratory syndrome coronavirus infection.

An indirect immunofluorescent assay (Euroimmun AG, Luebeck, Germany) was used to investigate the avidity of immunoglobulin G (IgG), IgM, IgA, and total Ig (IgGAM) antibody responses to severe acute respiratory syndrome coronavirus (SARS CoV) infections. Serial serum samples from eight patients collected during the first, third, and ninth months after the onset of infection were evaluated. It was found that low-avidity IgG antibodies were detected in 15/15 (100%), 1/5 (20%), and 0/8 (0%) serum samples collected during the first, third, and ninth months after the onset of symptoms, respectively. Low-avidity antibodies of IgA and IgM subclasses were detected in 14/14 (100%) and 3/14 (21%) serum samples, respectively, collected in the first month after the onset of infection. However, IgA antibodies remained low in avidity in a proportion of patients even during late convalescence. As a consequence, IgG antibody avidity assays gave better discrimination between acute-phase and late-convalescent-phase serum samples than IgM, IgA, or IgGAM assays. In two of these patients, sequential serum samples were also tested for IgG avidity against human CoV strains OC43 and 229E in parallel. While SARS CoV infections induced an anamnestic IgG antibody response to the 229E and OC43 viruses, these cross-reactive antibodies remained of high avidity from early (the first month) postinfection. The results showed that assays to detect low-avidity antibody may be useful for discriminating early from late antibody responses and also for distinguishing anamnestic cross-reactive antibody responses from primary specific responses. This may be useful in some clinical situations.

How far droplets can move in indoor environments--revisiting the Wells evaporation-falling curve.

UNLABELLED: A large number of infectious diseases are believed to be transmitted between people via large droplets and by airborne routes. An understanding of evaporation and dispersion of droplets and droplet nuclei is not only significant for developing effective engineering control methods for infectious diseases but also for exploring the basic transmission mechanisms of the infectious diseases. How far droplets can move is related to how far droplet-borne diseases can transmit. A simple physical model is developed and used here to investigate the evaporation and movement of droplets expelled during respiratory activities; in particular, the well-known Wells evaporation-falling curve of droplets is revisited considering the effect of relative humidity, air speed, and respiratory jets. Our simple model considers the movement of exhaled air, as well as the evaporation and movement of a single droplet. Exhaled air is treated as a steady-state non-isothermal (warm) jet horizontally issuing into stagnant surrounding air. A droplet is assumed to evaporate and move in this non-isothermal jet. Calculations are performed for both pure water droplets and droplets of sodium chloride (physiological saline) solution (0.9% w/v). We calculate the droplet lifetimes and how droplet size changes, as well as how far the droplets travel in different relative humidities. Our results indicate that a droplet's size predominately dictates its evaporation and movement after being expelled. The sizes of the largest droplets that would totally evaporate before falling 2 m away are determined under different conditions. The maximum horizontal distances that droplets can reach during different respiratory activities are also obtained. Our study is useful for developing effective prevention measures for controlling infectious diseases in hospitals and in the community at large. PRACTICAL IMPLICATIONS: Our study reveals that for respiratory exhalation flows, the sizes of the largest droplets that would totally evaporate before falling 2 m away are between 60 and 100 microm, and these expelled large droplets are carried more than 6 m away by exhaled air at a velocity of 50 m/s (sneezing), more than 2 m away at a velocity of 10 m/s (coughing) and less than 1 m away at a velocity of 1 m/s (breathing). These findings are useful for developing effective engineering control methods for infectious diseases, and also for exploring the basic transmission mechanisms of the infectious diseases. There is a need to examine the air distribution systems in hospital wards for controlling both airborne and droplet-borne transmitted diseases.

Comparative analytical sensitivities of six rapid influenza A antigen detection test kits for detection of influenza A subtypes H1N1, H3N2 and H5N1.

BACKGROUND: Rapid and simple methods for diagnosing human influenza A (H5N1) disease urgently needed. The limited data so far suggest that the currently available rapid antigen detection kits have poor clinical sensitivity for diagnosis of human H5N1 disease. OBJECTIVES: To compare the analytical sensitivity of six commercially available rapid antigen detection kits for the detection of "human" (subtypes H1N1, H3N2) and "avian" (subtype H5N1) influenza A viruses. STUDY DESIGN: Six commercially available test kits for the detection of influenza A were investigated. Analytic sensitivity for the detection of two contemporary H1N1, two H3N2 and three H5N1 viruses was determined using virus culture as a reference method. RESULTS AND CONCLUSIONS: Each test kit detected the H5N1 virus subtypes as efficiently as they detected conventional human viruses of subtypes H1N1 or H3N2. However, limits of detection of influenza viruses of all subtypes by antigen detection kits were >1000-fold lower than virus isolation. Thus, the reportedly poor clinical sensitivity of these antigen detection kits for diagnosis of patients with H5N1 disease is not due to a difference of sensitivity for detecting avian influenza H5N1 compared to human influenza viruses.

Behavioural considerations for hand hygiene practices: the basic building blocks.

Hand hygiene is considered to be the most effective measure to prevent microbial pathogen cross-transmission and healthcare-associated infections. In October 2005, the World Health Organization (WHO) World Alliance for Patient Safety launched the first Global Patient Safety Challenge 2005-2006, 'Clean Care is Safer Care', to tackle healthcare-associated infection on a large scale. Within the Challenge framework, international infection control experts and consultative taskforces met to develop new WHO Guidelines on Hand Hygiene in Healthcare. The taskforce was asked to explore aspects underlying hand hygiene behaviour that may influence its promotion among healthcare workers. The dynamics of behavioural change are complex and multi-faceted, but are of vital importance when designing a strategy to improve hand hygiene compliance. A reflection on challenges to be met and areas for future research are also proposed.