Contamination of Air and Surfaces in Workplaces with SARS-CoV-2 Virus: A Systematic Review

Multiplexed DNA and Protease Detection with Orthogonal Energy Transfer on a Single Quantum Dot Scaffolded Biosensor

Almost all pathogens, whether viral or bacterial, utilize key proteolytic steps in their pathogenesis. The ability to detect a pathogen's genomic material along with its proteolytic activity represents one approach to identifying the pathogen and providing initial evidence of its viability. Here, we report on a prototype biosensor design assembled around a single semiconductor quantum dot (QD) scaffold that is capable of detecting both nucleic acid sequences and proteolytic activity by using orthogonal energy transfer (ET) processes. The sensor consists of a central QD assembled via peptidyl-PNA linkers with multiple DNA sequences that encode complements to genomic sequences originating from the Ebola, Influenza, and COVID-19 viruses, which we use as surrogate targets. These are hybridized to complement strands labeled with a terbium (Tb) chelate, AlexaFluor647 (AF647), and Cy5.5 dyes, giving rise to two potential FRET cascades: the first includes Tb → QD → AF647 → Cy5.5 (→ = ET step), which is detected in a time-gated modality, and QD → AF647 → Cy5.5, which is detected from direct excitation. The labeled DNA-displaying QD construct is then further assembled with a RuII-modified peptide, which quenches QD photoluminescence by charge transfer and is recognized by a protease to yield the full biosensor. Each of the labeled DNAs and peptides can be ratiometrically assembled to the QD in a controllable manner to tune each of the ET pathways. Addition of a given target DNA displaces its labeled complement on the QD, disrupting that FRET channel, while protease addition disrupts charge transfer quenching of the central QD scaffold and boosts its photoluminescence and FRET relay capabilities. Along with characterizing the ET pathways and verifying biosensing in both individual and multiplexed formats, we also demonstrate the ability of this construct to function in molecular logic and perform Boolean operations; this highlights the construct's ability to discriminate and transduce signals between different inputs or pathogens. The potential application space for such a sensor device is discussed.

Surface sampling for SARS-CoV-2 RNA in workplace outbreak settings in the UK, 2021-22

AIMS

To utilize environmental surface sampling to evaluate areas of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contamination within workplaces to identify trends and improve local coronavirus disease 2019 (COVID-19) control measures.

METHODS AND RESULTS

Surface sampling was undertaken at 12 workplaces that experienced a cluster of COVID-19 cases in the workforce between March 2021 and March 2022. A total of 7.4% (61/829) samples collected were positive for SARS-CoV-2 RNA by the quantitative PCR (qPCR) with only 1.8% (15/829) of samples identified with crossing threshold (Ct) values <35.0. No sample returned whole-genome sequence inferring RNA detected was degraded.

CONCLUSIONS

Few workplace surface samples were positive for SARS-CoV-2 RNA and positive samples typically contained low levels of nucleic acid. Although these data may infer a low probability of fomite transmission within the workplace, Ct values may have been lower at the time of contamination. Workplace environmental sampling identified lapses in COVID-19 control measures within individual sites and showed trends throughout the pandemic.

NS, Víšová I, Vrabcová M, Houska M, Anthi J, Spasovová M, Mustacová J, Štěrba J, Dostálek J, Tung CP, Yang AS, Jack R, Dejneka A, Hajdu J, Vaisocherová-Lísalová H. Negligible risk of surface transmission of SARS-CoV-2 in public transportation

BACKGROUND

Exposure to pathogens in public transport systems is a common means of spreading infection, mainly by inhaling aerosol or droplets from infected individuals. Such particles also contaminate surfaces, creating a potential surface-transmission pathway.

METHODS

A fast acoustic biosensor with an antifouling nano-coating was introduced to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on exposed surfaces in the Prague Public Transport System. Samples were measured directly without pre-treatment. Results with the sensor gave excellent agreement with parallel quantitative reverse-transcription polymerase chain reaction (qRT-PCR) measurements on 482 surface samples taken from actively used trams, buses, metro trains and platforms between 7 and 9 April 2021, in the middle of the lineage Alpha SARS-CoV-2 epidemic wave when 1 in 240 people were COVID-19 positive in Prague.

RESULTS

Only ten of the 482 surface swabs produced positive results and none of them contained virus particles capable of replication, indicating that positive samples contained inactive virus particles and/or fragments. Measurements of the rate of decay of SARS-CoV-2 on frequently touched surface materials showed that the virus did not remain viable longer than 1-4 h. The rate of inactivation was the fastest on rubber handrails in metro escalators and the slowest on hard-plastic seats, window glasses and stainless-steel grab rails. As a result of this study, Prague Public Transport Systems revised their cleaning protocols and the lengths of parking times during the pandemic.

CONCLUSIONS

Our findings suggest that surface transmission played no or negligible role in spreading SARS-CoV-2 in Prague. The results also demonstrate the potential of the new biosensor to serve as a complementary screening tool in epidemic monitoring and prognosis.

Environmental sampling for SARS-CoV-2 in long term care facilities: lessons from a pilot study

Background: The SARS-CoV-2 pandemic has highlighted the risk of infection in long-term care facilities (LTCF) and the vulnerability of residents to severe outcomes. Environmental surveillance may help detect pathogens early and inform Infection Prevention and Control (IPC) measures in these settings. Methods: Upon notification of SARS-CoV-2 outbreaks, LTCF within a local authority in South West England were approached to take part in this pilot study. Investigators visited to swab common touch-points and elevated 'non-touch' surfaces (>1.5m above ground level) and samples were analysed for presence of SARS-CoV-2 genetic material (RNA). Data were collected regarding LTCF infrastructure, staff behaviours, clinical and epidemiological risk factors for infection (staff and residents), and IPC measures. Criteria for success were: recruitment of three LTCF; detection of SARS-COV-2 RNA; variation in proportion of SARS-CoV-2 positive surfaces by sampling zone; and collection of clinical and epidemiological data for context. Results: Three LTCFs were recruited, ranging in size and resident demographics. Outbreaks lasted 63, 50 and 30 days with resident attack rates of 53%, 40% and 8%, respectively. The proportion of sample sites on which SARS-CoV-2 was detected was highest in rooms occupied by infected residents and varied elsewhere in the LTCF, with low levels in a facility implementing enhanced IPC measures. The heterogeneity of settings and difficulty obtaining data made it unfeasible to assess association between environmental contamination and infection. A greater proportion of elevated surfaces tested positive for SARS-CoV-2 RNA than common touch-points. Conclusions: SARS-CoV-2 RNA can be detected in a variety of LTCF outbreak settings, both on common-touch items and in elevated sites out of reach. This suggests that further work is justified, to assess feasibility and utility of environmental sampling for infection surveillance in LTCF.

UVC-Based Air Disinfection Systems for Rapid Inactivation of SARS-CoV-2 Present in the Air

The World Health Organization (WHO) declared in May 2021 that SARS-CoV-2 is transmitted not only by close contact with infectious respiratory fluids from infected people or contaminated materials but also indirectly through air. Airborne transmission has serious implications for the control measures we can deploy, given the emergence of more transmissible variants. This emphasizes the need to deploy a mechanism to reduce the viral load in the air, especially in closed and crowded places such as hospitals, public transport buses, etc. In this study, we explored ultraviolet C (UVC) radiation for its ability to inactivate the SARS-CoV-2 particles present in aerosols and designed an air disinfection system to eliminate infectious viruses. We studied the virus inactivation kinetics to identify the UVC dosage required to achieve maximum virus inactivation. Based on the experimental data, UVC-based devices were designed for the sanitization of air through HVAC systems in closed spaces. Further, a risk assessment model to estimate the risk reduction was applied which showed that the use of UVC radiation could result in the reduction of the risk of infection in occupied spaces by up to 90%.

Measurement of SARS-CoV-2 in air and on surfaces in Scottish hospitals

BACKGROUND

There are still uncertainties in our knowledge of the amount of SARS-CoV-2 virus present in the environment - where it can be found, and potential exposure determinants - limiting our ability to effectively model and compare interventions for risk management.

AIM

This study measured SARS-CoV-2 in three hospitals in Scotland on surfaces and in air, alongside ventilation and patient care activities.

METHODS

Air sampling at 200 L/min for 20 min and surface sampling were performed in two wards designated to treat COVID-19-positive patients and two non-COVID-19 wards across three hospitals in November and December 2020.

FINDINGS

Detectable samples of SARS-CoV-2 were found in COVID-19 treatment wards but not in non-COVID-19 wards. Most samples were below assay detection limits, but maximum concentrations reached 1.7×10³ genomic copies/m³ in air and 1.9×10⁴ copies per surface swab (3.2×10² copies/cm² for surface loading). The estimated geometric mean air concentration (geometric standard deviation) across all hospitals was 0.41 (71) genomic copies/m³ and the corresponding values for surface contamination were 2.9 (29) copies/swab. SARS-CoV-2 RNA was found in non-patient areas (patient/visitor waiting rooms and personal protective equipment changing areas) associated with COVID-19 treatment wards.

CONCLUSION

Non-patient areas of the hospital may pose risks for infection transmission and further attention should be paid to these areas. Standardization of sampling methods will improve understanding of levels of environmental contamination. The pandemic has demonstrated a need to review and act upon the challenges of older hospital buildings meeting current ventilation guidance.

SARS-CoV-2 in the Air Surrounding Patients during Nebulizer Therapy

Nebulizer therapy is commonly used for patients with obstructive pulmonary disease or acute pulmonary infections with signs of obstruction. It is considered a “potential aerosol-generating procedure,” and the risk of disease transmission to health care workers is uncertain. The aim of this pilot study was to assess whether nebulizer therapy in hospitalized COVID-19 patients is associated with increased dispersion of SARS-CoV-2. Air samples collected prior to and during nebulizer therapy were analyzed by RT-PCR and cell culture. Total aerosol particle concentrations were also quantified. Of 13 patients, seven had quantifiable virus in oropharynx samples, and only two had RT-PCR positive air samples. For both these patients, air samples collected during nebulizer therapy had higher SARS-CoV-2 RNA concentrations compared to control air samples. Also, for particle sizes 0.3–5 µm, particle concentrations were significantly higher during nebulizer therapy than in controls. We were unable to cultivate virus from any of the RT-PCR positive air samples, and it is therefore unknown if the detected virus were replication-competent; however, the significant increase in smaller particles, which can remain airborne for extended periods of time, and increased viral RNA concentrations during treatment may indicate that nebulizer therapy is associated with increased risk of SARS-CoV-2 transmission.

Detection of SARS-CoV-2 in Air and on Surfaces in Rooms of Infected Nursing Home Residents

There is an ongoing debate on airborne transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) as a risk factor for infection. In this study, the level of SARS-CoV-2 in air and on surfaces of SARS-CoV-2 infected nursing home residents was assessed to gain insight in potential transmission routes. During outbreaks, air samples were collected using three different active and one passive air sampling technique in rooms of infected patients. Oropharyngeal swabs (OPS) of the residents and dry surface swabs were collected. Additionally, longitudinal passive air samples were collected during a period of 4 months in common areas of the wards. Presence of SARS-CoV-2 RNA was determined using RT-qPCR, targeting the RdRp- and E-genes. OPS, samples of two active air samplers and surface swabs with Ct-value ≤35 were tested for the presence of infectious virus by cell culture. In total, 360 air and 319 surface samples from patient rooms and common areas were collected. In rooms of 10 residents with detected SARS-CoV-2 RNA in OPS, SARS-CoV-2 RNA was detected in 93 of 184 collected environmental samples (50.5%) (lowest Ct 29.5), substantially more than in the rooms of residents with negative OPS on the day of environmental sampling (n = 2) (3.6%). SARS-CoV-2 RNA was most frequently present in the larger particle size fractions [>4 μm 60% (6/10); 1-4 μm 50% (5/10); <1 μm 20% (2/10)] (Fischer exact test P = 0.076). The highest proportion of RNA-positive air samples on room level was found with a filtration-based sampler 80% (8/10) and the cyclone-based sampler 70% (7/10), and impingement-based sampler 50% (5/10). SARS-CoV-2 RNA was detected in 10 out of 12 (83%) passive air samples in patient rooms. Both high-touch and low-touch surfaces contained SARS-CoV-2 genome in rooms of residents with positive OPS [high 38% (21/55); low 50% (22/44)]. In one active air sample, infectious virus in vitro was detected. In conclusion, SARS-CoV-2 is frequently detected in air and on surfaces in the immediate surroundings of room-isolated COVID-19 patients, providing evidence of environmental contamination. The environmental contamination of SARS-CoV-2 and infectious aerosols confirm the potential for transmission via air up to several meters.

SARS-CoV-2 in Atmospheric Particulate Matter: An Experimental Survey in the Province of Venice in Northern Italy

Analysis of atmospheric particulate matter (PM) has been proposed for the environmental surveillance of SARS-CoV-2. The aim of this study was to increase the current knowledge about the occurrence of SARS-CoV-2 in atmospheric PM, introduce a dedicated sampling method, and perform a simultaneous assessment of human seasonal coronavirus 229E. Thirty-two PM samples were collected on quartz fiber filters and six on Teflon using a low- and high-volumetric rate sampler, respectively, adopting a novel procedure for optimized virus detection. Sampling was performed at different sites in the Venice area (Italy) between 21 February and 8 March 2020 (n = 16) and between 27 October and 25 November 2020 (n = 22). A total of 14 samples were positive for Coronavirus 229E, 11 of which were collected in October–November 2020 (11/22; positivity rate 50%) and 3 in February–March 2020 (3/16 samples, 19%). A total of 24 samples (63%) were positive for SARS-CoV-2. Most of the positive filters were collected in October–November 2020 (19/22; positivity rate, 86%), whereas the remaining five were collected in February–March 2020 at two distinct sites (5/16, 31%). These findings suggest that outdoor PM analysis could be a promising tool for environmental surveillance. The results report a low concentration of SARS-CoV-2 in outdoor air, supporting a scarce contribution to the spread of infection.

Investigation of a SARS-CoV-2 Outbreak at an Automotive Manufacturing Site in England

Workplace-related outbreaks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to occur globally. The manufacturing sector presents a particular concern for outbreaks, and a better understanding of transmission risks are needed. Between 9 March and 24 April 2021, the COVID-19 (coronavirus disease 2019) Outbreak Investigation to Understand Transmission (COVID-OUT) study undertook a comprehensive investigation of a SARS-CoV-2 outbreak at an automotive manufacturing site in England. The site had a total of 266 workers, and 51 SARS-CoV-2 infections. Overall, ventilation, humidity, and temperature at the site were assessed to be appropriate for the number of workers and the work being conducted. The company had implemented a number of infection control procedures, including provision of face coverings, spacing in the work, and welfare areas to allow for social distancing. However, observations of worker practices identified lapses in social distancing, although all were wearing face coverings. A total of 38 workers, including four confirmed cases, participated in the COVID-OUT study. The majority of participants received COVID-19 prevention training, though 42.9% also reported that their work required close physical contact with co-workers. Additionally, 73.7% and 34.2% had concerns regarding reductions in future income and future unemployment, respectively, due to self-isolation. This investigation adds to the growing body of evidence of SARS-CoV-2 outbreaks from the manufacturing sector. Despite a layered COVID-19 control strategy at this site, cases clustered in areas of high occupancy and close worker proximity.

A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission

Airborne transmission of SARS-CoV-2 has been object of debate in the scientific community since the beginning of COVID-19 pandemic. This mechanism of transmission could arise from virus-laden aerosol released by infected individuals and it is influenced by several factors. Among these, the concentration and size distribution of virus-laden particles play an important role. The knowledge regarding aerosol transmission increases as new evidence is collected in different studies, even if it is not yet available a standard protocol regarding air sampling and analysis, which can create difficulties in the interpretation and application of results. This work reports a systematic review of current knowledge gained by 73 published papers on experimental determination of SARS-CoV-2 RNA in air comparing different environments: outdoors, indoor hospitals and healthcare settings, and public community indoors. Selected papers furnished 77 datasets: outdoor studies (9/77, 11.7%) and indoor studies (68/77. 88.3%). The indoor datasets in hospitals were the vast majority (58/68, 85.3%), and the remaining (10/68, 14.7%) were classified as community indoors. The fraction of studies having positive samples, as well as positivity rates (i.e. ratios between positive and total samples) are significantly larger in hospitals compared to the other typologies of sites. Contamination of surfaces was more frequent (in indoor datasets) compared to contamination of air samples; however, the average positivity rate was lower compared to that of air. Concentrations of SARS-CoV-2 RNA in air were highly variables and, on average, lower in outdoors compared to indoors. Among indoors, concentrations in community indoors appear to be lower than those in hospitals and healthcare settings.

Dispersion of SARS-CoV-2 in air surrounding COVID-19-infected individuals with mild symptoms

Since the beginning of the pandemic, the transmission modes of SARS-CoV-2-particularly the role of aerosol transmission-have been much debated. Accumulating evidence suggests that SARS-CoV-2 can be transmitted by aerosols, and not only via larger respiratory droplets. In this study, we quantified SARS-CoV-2 in air surrounding 14 test subjects in a controlled setting. All subjects had SARS-CoV-2 infection confirmed by a recent positive PCR test and had mild symptoms when included in the study. RT-PCR and cell culture analyses were performed on air samples collected at distances of one, two, and four meters from test subjects. Oronasopharyngeal samples were taken from consenting test subjects and analyzed by RT-PCR. Additionally, total aerosol particles were quantified during air sampling trials. Air viral concentrations at one-meter distance were significantly correlated with both viral loads in the upper airways, mild coughing, and fever. One sample collected at four-meter distance was RT-PCR positive. No samples were successfully cultured. The results reported here have potential application for SARS-CoV-2 detection and monitoring schemes, and for increasing our understanding of SARS-CoV-2 transmission dynamics. Practical implications. In this study, quantification of SARS-CoV-2 in air was performed around infected persons with mild symptoms. Such persons may go longer before they are diagnosed and may thus be a disproportionately important epidemiological group. By correlating viral concentrations in air with behavior and symptoms, we identify potential risk factors for viral dissemination in indoor environments. We also show that quantification of total aerosol particles is not a useful strategy for monitoring SARS-CoV-2 in indoor environments.

Transmission of Respiratory Viral Diseases to Health Care Workers: COVID-19 as an Example

Health care workers (HCWs) can acquire infectious diseases, including coronavirus disease 2019 (COVID-19), from patients. Herein, COVID-19 is used with the source–pathway–receptor framework as an example to assess evidence for the role of aerosol transmission and indirect contact transmission of viral respiratory infectious diseases. Evidence for both routes is strong for COVID-19 and other respiratory viruses, but aerosol transmission is likely dominant for COVID-19. Key knowledge gaps about transmission processes and control strategies include the distribution of viable virus among respiratory aerosols of different sizes, the mechanisms and efficiency by which virus deposited on the facial mucous membrane moves to infection sites inside the body, and the performance of source controls such as face coverings and aerosol containment devices. To ensure that HCWs are adequately protected from infection, guidelines and regulations must be updated to reflect the evidence that respiratory viruses are transmitted via aerosols.

Expected final online publication date for the Annual Review of Public Health, Volume 43 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Expert elicitation on the relative importance of possible SARS-CoV-2 transmission routes and the effectiveness of mitigations

OBJECTIVES

To help people make decisions about the most effective mitigation measures against SARS-CoV-2 transmission in different scenarios, the likelihoods of transmission by different routes need to be quantified to some degree (however uncertain). These likelihoods need to be communicated in an appropriate way to illustrate the relative importance of different routes in different scenarios, the likely effectiveness of different mitigation measures along those routes, and the level of uncertainty in those estimates. In this study, a pragmatic expert elicitation was undertaken to supply the underlying quantitative values to produce such a communication tool.

PARTICIPANTS

Twenty-seven individual experts from five countries and many scientific disciplines provided estimates.

OUTCOME MEASURES

Estimates of transmission parameters, assessments of the quality of the evidence, references to relevant literature, rationales for their estimates and sources of uncertainty.

RESULTS AND CONCLUSION

The participants' responses showed that there is still considerable disagreement among experts about the relative importance of different transmission pathways and the effectiveness of different mitigation measures due to a lack of empirical evidence. Despite these disagreements, when pooled, the majority views on each parameter formed an internally consistent set of estimates (for example, that transmission was more likely indoors than outdoors, and at closer range), which formed the basis of a visualisation to help individuals and organisations understand the factors that influence transmission and the potential benefits of different mitigation measures.

Surface and air contamination with SARS-CoV-2 from hospitalized COVID-19 patients in Toronto, Canada, March-May 2020

Background

We determined the burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in air and on surfaces in rooms of patients hospitalized with coronavirus disease 2019 (COVID-19) and investigated patient characteristics associated with SARS-CoV-2 environmental contamination.

Methods

Nasopharyngeal swabs, surface, and air samples were collected from the rooms of 78 inpatients with COVID-19 at 6 acute care hospitals in Toronto from March to May 2020. Samples were tested for SARS-CoV-2 ribonucleic acid (RNA), cultured to determine potential infectivity, and whole viral genomes were sequenced. Association between patient factors and detection of SARS-CoV-2 RNA in surface samples were investigated.

Results

Severe acute respiratory syndrome coronavirus 2 RNA was detected from surfaces (125 of 474 samples; 42 of 78 patients) and air (3 of 146 samples; 3 of 45 patients); 17% (6 of 36) of surface samples from 3 patients yielded viable virus. Viral sequences from nasopharyngeal and surface samples clustered by patient. Multivariable analysis indicated hypoxia at admission, polymerase chain reaction-positive nasopharyngeal swab (cycle threshold of ≤30) on or after surface sampling date, higher Charlson comorbidity score, and shorter time from onset of illness to sampling date were significantly associated with detection of SARS-CoV-2 RNA in surface samples.

Conclusions

The infrequent recovery of infectious SARS-CoV-2 virus from the environment suggests that the risk to healthcare workers from air and near-patient surfaces in acute care hospital wards is likely limited.

Room HVAC Influences on the Removal of Airborne Particulate Matter: Implications for School Reopening during the COVID-19 Pandemic

(1) Background: Many schools and higher education settings have confronted the issue of reopening their facilities after the COVID-19 pandemic. In response, several airflow strategies spanning from adding portable air purifiers to major mechanical overhauls have been suggested to equip classrooms with what is necessary to provide a safe and reliable environment. Yet, there are many unknowns about specific contributions of the building system and its design and performance on indoor air quality (IAQ) improvements. (2) Methods: this study examined the combined effect of ventilation type, airflow rates, and filtration on IAQ in five different classrooms. Experiments were conducted by releasing inert surrogate particles into the classrooms and measuring the concentrations in various locations of the room. (3) Results: we showed that while the distribution of particles in the space is a complex function of space geometry and air distribution configurations, the average decay rate of contaminants is proportional to the number of air changes per hour in the room. (4) Conclusions: rooms with a central HVAC system responded quicker to an internal source of contamination than rooms with only fan coil units. Furthermore, increasing the ventilation rate without improved filtration is an inefficient use of energy.

Environmental screening for SARS-CoV-2 in long term care facilities: lessons from a pilot study

Background: The SARS-CoV-2 pandemic has highlighted the risk of infection transmission in long-term care facilities (LTCF) and the vulnerability of resident populations. It is essential to understand the environmental spread of the virus and risk of indirect transmission to inform Infection Prevention and Control (IPC) measures in these settings. Methods: Upon notification of SARS-CoV-2 outbreaks, LTCF within a local authority in the South West of England were approached to take part in this pilot study. Investigators visited to swab common touch-points and elevated ‘non-touch’ surfaces and samples were analysed for presence of SARS-CoV-2 genetic material (RNA). Data were collected regarding LTCF infrastructure, staff behaviours, clinical and epidemiological risk factors for infection (staff and residents), and IPC measures. Criteria for success were: recruitment of three LTCF; detection of SARS-COV-2 RNA; variation in proportion of SARS-CoV-2 positive surfaces by sampling zone; potential to assess infection risk from SARS-CoV-2 positive surfaces. Results: Three LTCFs were recruited, ranging in size and resident demographics. Outbreaks lasted 63, 50 and 30 days with resident attack rates of 53%, 40% and 8%, respectively. The proportion of sample sites on which SARS-CoV-2 was detected was highest in rooms occupied by infected residents and varied elsewhere in the LTCF, with low levels in a facility implementing enhanced IPC measures. The heterogeneity of settings and difficulty obtaining data made it difficult to assess association between environmental contamination and infection. Elevated surfaces were more likely to test positive for SARS-CoV-2 RNA than common touch-points. Conclusions: SARS-CoV-2 RNA can be detected in a variety of LTCF outbreak settings. We identified variation in environmental spread which could be associated with implementation of IPC measures, though we were unable to assess the impact on infection risk. Sampling elevated surfaces could add to ongoing public health surveillance for SARS-CoV-2 and other airborne pathogens in LTCF.

The Development of a Covid-19 Control Measures Risk Matrix for Occupational Hygiene Protective Measures

The British Occupational Hygiene Society (BOHS) Covid-19 Working Group developed a control banding matrix to provide guidance for employers and others to help assess the risks of Covid-19 infection during the pandemic. The matrix was based on occupational hygiene principles and the judgement of the occupational health practitioners involved; since objective data on workers’ exposure were unavailable. Users of the matrix identify one of five exposure categories based on generic job descriptions and example occupations, and these categories are linked to generic guidance on interventions at source, on the exposure pathway and for individual workers. The risk matrix was published on the BOHS website and the guidance has been downloaded more than 2000 times. The matrix has had limited evaluation for reliability, but the data suggest that the highest exposure ranked jobs were associated with higher age-standardized mortality in Britain during the pandemic. However, there was considerable variability in exposure assignments between assessors, which underlines the need for the control guidance to be precautionary. The BOHS calls on academic researchers to undertake further work to validate the reliability of the tool.

SARS-CoV-2 and the role of fomite transmission: a systematic review

Background: SARS-CoV-2 has been detected in fomites which suggests the virus could be transmitted via inanimate objects. However, there is uncertainty about the mechanistic pathway for such transmissions. Our objective was to identify, appraise and summarise the evidence from primary studies and systematic reviews assessing the role of fomites in transmission.  Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, and Google Scholar; assess study quality based on five criteria and report important findings on an ongoing basis. Results: We found 64 studies: 63 primary studies and one systematic review (n=35). The settings for primary studies were predominantly in hospitals (69.8%) including general wards, ICU and SARS-CoV-2 isolation wards. There were variations in the study designs including timing of sample collection, hygiene procedures, ventilation settings and cycle threshold. The overall quality of reporting was low to moderate. The frequency of positive SARS-CoV-2 tests across 51 studies (using RT-PCR) ranged from 0.5% to 75%. Cycle threshold values ranged from 20.8 to 44.1. Viral concentrations were reported in 17 studies; however, discrepancies in the methods for estimation prevented comparison. Eleven studies (17.5%) attempted viral culture, but none found a cytopathic effect. Results of the systematic review showed that healthcare settings were most frequently tested (25/35, 71.4%), but laboratories reported the highest frequency of contaminated surfaces (20.5%, 17/83).  Conclusions: The majority of studies report identification of SARS-CoV-2 RNA on inanimate surfaces; however, there is a lack of evidence demonstrating the recovery of viable virus. Lack of positive viral cultures and variation in cycle thresholds create uncertainty about fomites as a mode of transmission. Heterogeneity in study designs and methodology prevents comparisons of findings across studies. Standardized guidelines for conducting and reporting research on fomite transmission is warranted.

SARS-CoV-2 and the role of fomite transmission: a systematic review

Background: SARS-CoV-2 RNA has been detected in fomites which suggests the virus could be transmitted via inanimate objects. However, there is uncertainty about the mechanistic pathway for such transmissions. Our objective was to identify, appraise and summarise the evidence from primary studies and systematic reviews assessing the role of fomites in transmission.  Methods: This review is part of an Open Evidence Review on Transmission Dynamics of SARS-CoV-2. We conduct ongoing searches using WHO Covid-19 Database, LitCovid, medRxiv, and Google Scholar; assess study quality based on five criteria and report important findings on an ongoing basis. Results: We found 64 studies: 63 primary studies and one systematic review (n=35). The settings for primary studies were predominantly in hospitals (69.8%) including general wards, ICU and SARS-CoV-2 isolation wards. There were variations in the study designs including timing of sample collection, hygiene procedures, ventilation settings and cycle threshold. The overall quality of reporting was low to moderate. The frequency of positive SARS-CoV-2 tests across 51 studies (using RT-PCR) ranged from 0.5% to 75%. Cycle threshold values ranged from 20.8 to 44.1. Viral concentrations were reported in 17 studies; however, discrepancies in the methods for estimation prevented comparison. Eleven studies (17.5%) attempted viral culture, but none found a cytopathic effect. Results of the systematic review showed that healthcare settings were most frequently tested (25/35, 71.4%), but laboratories reported the highest frequency of contaminated surfaces (20.5%, 17/83).  Conclusions: The majority of studies report identification of SARS-CoV-2 RNA on inanimate surfaces; however, there is a lack of evidence demonstrating the recovery of viable virus. Lack of positive viral cultures suggests that the risk of transmission of SARS-CoV-2 through fomites is low. Heterogeneity in study designs and methodology prevents comparisons of findings across studies. Standardized guidelines for conducting and reporting research on fomite transmission is warranted.