Risks of Infection with SARS-CoV-2 Due to Contaminated Surfaces: A Scoping Review

A narrative review of alternative transmission routes of COVID 19: what we know so far

The Coronavirus disease 19 (COVID-19) pandemics, caused by severe acute respiratory syndrome coronaviruses, SARS-CoV-2, represent an unprecedented public health challenge. Beside person-to-person contagion via airborne droplets and aerosol, which is the main SARS-CoV-2's route of transmission, alternative modes, including transmission via fomites, food and food packaging, have been investigated for their potential impact on SARS-CoV-2 diffusion. In this context, several studies have demonstrated the persistence of SARS-CoV-2 RNA and, in some cases, of infectious particles on exposed fomites, food and water samples, confirming their possible role as sources of contamination and transmission. Indeed, fomite-to-human transmission has been demonstrated in a few cases where person-to-person transmission had been excluded. In addition, recent studies supported the possibility of acquiring COVID-19 through the fecal-oro route; the occurrence of COVID-19 gastrointestinal infections, in the absence of respiratory symptoms, also opens the intriguing possibility that these cases could be directly related to the ingestion of contaminated food and water. Overall, most of the studies considered these alternative routes of transmission of low epidemiological relevance; however, it should be considered that they could play an important role, or even be prevalent, in settings characterized by different environmental and socio-economic conditions. In this review, we discuss the most recent findings regarding SARS-CoV-2 alternative transmission routes, with the aim to disclose what is known about their impact on COVID-19 spread and to stimulate research in this field, which could potentially have a great impact, especially in low-resource contexts.

Environmental dissemination of respiratory viruses: dynamic interdependencies of respiratory droplets, aerosols, aerial particulates, environmental surfaces, and contribution of viral re-aerosolization

During the recent pandemic of COVID-19 (SARS-CoV-2), influential public health agencies such as the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have favored the view that SARS CoV-2 spreads predominantly via droplets. Many experts in aerobiology have openly opposed that stance, forcing a vigorous debate on the topic. In this review, we discuss the various proposed modes of viral transmission, stressing the interdependencies between droplet, aerosol, and fomite spread. Relative humidity and temperature prevailing determine the rates at which respiratory aerosols and droplets emitted from an expiratory event (sneezing, coughing, etc.) evaporate to form smaller droplets or aerosols, or experience hygroscopic growth. Gravitational settling of droplets may result in contamination of environmental surfaces (fomites). Depending upon human, animal and mechanical activities in the occupied space indoors, viruses deposited on environmental surfaces may be re-aerosolized (re-suspended) to contribute to aerosols, and can be conveyed on aerial particulate matter such as dust and allergens. The transmission of respiratory viruses may then best be viewed as resulting from dynamic virus spread from infected individuals to susceptible individuals by various physical states of active respiratory emissions, instead of the current paradigm that emphasizes separate dissemination by respiratory droplets, aerosols or by contaminated fomites. To achieve the optimum outcome in terms of risk mitigation and infection prevention and control (IPAC) during seasonal infection peaks, outbreaks, and pandemics, this holistic view emphasizes the importance of dealing with all interdependent transmission modalities, rather than focusing on one modality.

RNA extraction-free workflow integrated with a single-tube CRISPR-Cas-based colorimetric assay for rapid SARS-CoV-2 detection in different environmental matrices

On-site environmental surveillance of viruses is increasingly important for infection prevention and pandemic control. Herein, we report a facile single-tube colorimetric assay for detecting severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from environmental compartments. Using glycerol as the phase separation additive, reverse transcription recombinase polymerase amplification (RT-RPA), CRISPR-Cas system activation, G-quadruplex (G4) cleavage, and G4-based colorimetric reaction were performed in a single tube. To further simplify the test, viral RNA genomes used for the one-tube assay were obtained via acid/base treatment without further purification. The whole assay from sampling to visual readout was completed within 30 min at a constant temperature without the need for sophisticated instruments. Coupling the RT-RPA to CRISPR-Cas improved the reliability by avoiding false positive results. Non-labeled cost-effective G4-based colorimetric systems are highly sensitive to CRISPR-Cas cleavage events, and the proposed assay reached the limit of detection of 0.84 copies/µL. Moreover, environmental samples from contaminated surfaces and wastewater were analyzed using this facile colorimetric assay. Given its simplicity, sensitivity, specificity, and cost-effectiveness, our proposed colorimetric assay is highly promising for applications in on-site environmental surveillance of viruses.

Mitigation of SARS-CoV-2 by Using Transition Metal Nanozeolites and Quaternary Ammonium Compounds as Antiviral Agents in Suspensions and Soft Fabric Materials

Introduction

The coronavirus disease 2019 (COVID-19) pandemic has demonstrated the need for novel, affordable, and efficient reagents to help reduce viral transmission, especially in high-risk environments including medical treatment facilities, close quarters, and austere settings. We examined transition-metal nanozeolite suspensions and quaternary ammonium compounds as an antiviral surface coating for various textile materials.

Methods

Zeolites are crystalline porous aluminosilicate materials, with the ability of ion-exchanging different cations. Nanozeolites (30 nm) were synthesized and then ion-exchanged with silver, zinc and copper ions. Benzalkonium nitrate (BZN) was examined as the quaternary ammonium ion (quat). Suspensions of these materials were tested for antiviral activity towards SARS-CoV-2 using plaque assay and immunostaining. Suspensions of the nanozeolite and quat were deposited on polyester and cotton fabrics and the ability of these textiles towards neutralizing SARS-CoV-2 was examined.

Results

We hypothesized that transition metal ion containing zeolites, particularly silver and zinc (AM30) and silver and copper (AV30), would be effective in reducing the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Additionally, AM30 and AV30 antiviral potency was tested when combined with a quaternary ammonium carrier, BZN. Our results indicate that exposure of SARS-CoV-2 to AM30 and/or AV30 suspensions reduced viral loads with time and exhibited dose-dependence. Antiviral activities of the combination of zeolite and BZN compositions were significantly enhanced. When used in textiles, AM30 and AV30-coated cotton and polyester fabrics alone or in combination with BZN exhibited significant antiviral properties, which were maintained even after various stress tests, including washes, SARS-CoV-2-repeated exposures, or treatments with soil-like materials.

Conclusion

This study shows the efficacy of transition metal nanozeolite formulations as novel antiviral agents and establishes that nanozeolite with silver and zinc ions (AM30) and nanozeolite with silver and copper ions (AV30) when combined with benzalkonium nitrate (BZN) quickly and continuously inactivate SARS-CoV-2 in suspension and on fabric materials.

Spread of viruses, which measures are the most apt to control COVID-19?

The persistent debate about the modes of transmission of SARS-CoV2 and preventive measures has illustrated the limits of our knowledge regarding the measures to be implemented in the face of viral risk. Past and present (pandemic-related) scientific data underline the complexity of the phenomenon and its variability over time. Several factors contribute to the risk of transmission, starting with incidence in the general population (i.e., colonization pressure) and herd immunity. Other major factors include intensity of symptoms, interactions with the reservoir (proximity and duration of contact), the specific characteristics of the virus(es) involved, and a number of unpredictable elements (humidity, temperature, ventilation…). In this review, we will emphasize the difficulty of "standardizing" the situations that might explain the discrepancies found in the literature. We will show that the airborne route remains the main mode of transmission. Regarding preventive measures of prevention, while vaccination remains the cornerstone of the fight against viral outbreaks, we will remind the reader that wearing a mask is the main barrier measure and that the choice of type of mask depends on the risk situations. Finally, we believe that the recent pandemic should induce us in the future to modify our recommendations by adapting our measures in hospitals, not to the pathogen concerned, which is currently the case, but rather to the type of at-risk situation.

A visible-light activated ROS generator multilayer film for antibacterial coatings

The current scenario of antibiotic-resistant bacteria and pandemics caused by viruses makes research in the area of antibacterial and antiviral materials and surfaces more urgent than ever. In this regard, salicylideneimine based tetracoordinate boron-containing organic compounds are emerging as a new class of photosensitizers for singlet oxygen generation. However, the inherent inability of small organic molecules to be processed limits their potential use in functional coatings. Here we show the synthesis of a novel polymer functionalized with diiodosalicylideneimine-boron difluoride (PEI-BF2) and its utility for surface coating inside glass vials via layer-by-layer (LbL) assembly. The multilayer thin films are characterized using AFM and UV-Vis spectroscopy and the resultant coatings display excellent stability. The multilayer coating could be activated using visible light, and owing to the photocatalytic activity of the incorporated PEI-BF2, the surface coating is able to generate singlet oxygen efficiently upon light irradiation. Further, the multilayer coated surfaces exhibit remarkable antimicrobial activity towards both Gram-positive and Gram-negative bacteria under a variety of conditions. Thus, owing to the simple synthesis and the convenient methodology adopted for the preparation of multilayer coatings, the material reported here could pave the way for the development of sunlight activated large area self-sterile surfaces.

A Novel Application of Risk-Risk Tradeoffs in Occupational Health: Nurses' Occupational Asthma and Infection Risk Perceptions Related to Cleaning and Disinfection during COVID-19

BACKGROUND

Nurses face the risk of new onset occupational asthma (OA) due to exposures to cleaning and disinfection (C&D) agents used to prevent infections in healthcare facilities. The objective of this study was to measure nurses' preferences when presented with simultaneous OA and respiratory viral infection (e.g., COVID-19) risks related to increased/decreased C&D activities.

METHODS

Nurses working in healthcare for ≥1 year and without physician-diagnosed asthma were recruited for an online anonymous survey, including four risk-risk tradeoff scenarios between OA and respiratory infection with subsequent recovery (Infect and Recovery) or subsequent death (Infect and Death). Nurses were presented with baseline risks at hypothetical "Hospital 1", and were asked to choose Hospital 2 (increased OA risk to maintain infection risk), Hospital 3 (increased infection risk to maintain OA risk), or indicate that they were equally happy.

RESULTS

Over 70% of nurses were willing to increase infection risk to maintain baseline OA risk if they were confident they would recover from the infection. However, even when the risk of infection leading to death was much lower than OA, most nurses were not willing to accept a larger (but still small) risk of death to avoid doubling their OA risk. Age, work experience, and ever having contracted or knowing anyone who has contracted a respiratory viral infection at work influenced choices.

CONCLUSIONS

We demonstrate the novel application of a risk-risk tradeoff framework to address an occupational health issue. However, more data are needed to test the generalizability of the risk preferences found in this specific risk-risk tradeoff context.

Real-World Effectiveness of Mix-and-Match Vaccine Regimens against SARS-CoV-2 Delta Variant in Thailand: A Nationwide Test-Negative Matched Case-Control Study

The objective of this study is to explore the real-world effectiveness of various vaccine regimens to tackle the epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant in Thailand during September–December 2021. We applied a test-negative case control study, using nationwide records of people tested for SARS-CoV-2. Each case was matched with two controls with respect to age, detection date, and specimen collection site. A conditional logistic regression was performed. Results were presented in the form vaccine effectiveness (VE) and 95% confidence interval. A total of 1,460,458 observations were analyzed. Overall, the two-dose heterologous prime-boost, ChAdOx1 + BNT162b2 and CoronaVac + BNT162b2, manifested the largest protection level (79.9% (74.0–84.5%) and 74.7% (62.8–82.8%)) and remained stable over the whole study course. The three-dose schedules (CoronaVac + CoronaVac + ChAdOx1, and CoronaVac + CoronaVac + BNT162b2) expressed very high degree of VE estimate (above 80.0% at any time interval). Concerning severe infection, almost all regimens displayed very high VE estimate. For the two-dose schedules, heterologous prime-boost regimens seemed to have slightly better protection for severe infection relative to homologous regimens. Campaigns to expedite the rollout of third-dose booster shot should be carried out. Heterologous prime-boost regimens should be considered as an option to enhance protection for the entire population.

Emerging SARS-CoV-2 Mutational Variants of Concern Should Not Vary in Susceptibility to Microbicidal Actives

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is evolving, with emergence of mutational variants due to the error-prone replication process of RNA viruses, in general. More recently, the Delta and Omicron variants (including sub-variants BA.1-5) predominate globally, and a Delta-Omicron recombinant termed Deltacron has emerged. The emergence of variants of concern (VOC) demonstrating immune evasion and potentially greater transmissibility and virulence naturally raises concern in both the infection control communities and the public at large, as to the continued suitability of interventions intended to mitigate the risk of viral dissemination and acquisition of the associated disease COVID-19. We evaluated the virucidal efficacy of targeted surface hygiene products (an ethanol/quaternary ammonium compound (QAC)-containing disinfectant spray, a QAC disinfectant wipe, a lactic acid disinfectant wipe, and a citric acid disinfectant wipe) through both theoretical arguments and empirical testing using international standard methodologies (ASTM E1053-20 hard surface test and EN14476:2013+A2:2019 suspension test) in the presence of soil loads simulating patients' bodily secretions/excretions containing shed virus. The results demonstrate, as expected, complete infectious viral inactivation (≥3.0 to ≥4.7 log₁₀ reduction in infectious virus titer after as little as 15 s contact time at room temperature) by these surface hygiene agents of the original SARS-CoV-2 isolate and its Beta and Delta VOC. Through appropriate practices of targeted surface hygiene, it is expected that irrespective of the SARS-CoV-2 VOC encountered as the current pandemic unfolds (and, for that matter, any emerging and/or re-emerging enveloped virus), the chain of infection from virus-contaminated fomites to the hand and mucous membranes of a susceptible person may be disrupted.

Forecasted Trends of the New COVID-19 Epidemic Due to the Omicron Variant in Thailand, 2022

Thailand is among many countries severely affected by COVID-19 since the beginning of the global pandemic. Thus, a deliberate planning of health care resource allocation against health care demand in light of the new SARS-CoV-2 variant, Omicron, is crucial. This study aims to forecast the trends in COVID-19 cases and deaths from the Omicron variant in Thailand. We used a compartmental susceptible-exposed-infectious-recovered model combined with a system dynamics model. We developed four scenarios with differing values of the reproduction number (R) and vaccination rates. In the most pessimistic scenario (R = 7.5 and base vaccination rate), the number of incident cases reached a peak of 49,523 (95% CI: 20,599 to 99,362) by day 73, and the peak daily deaths grew to 270 by day 50. The predicted cumulative cases and deaths at the end of the wave were approximately 3.7 million and 22,000, respectively. In the most optimistic assumption (R = 4.5 and speedy vaccination rate), the peak incident cases was about one third the cases in the pessimistic assumption (15,650, 95% CI: 12,688 to 17,603). In the coming months, Thailand may face a new wave of the COVID-19 epidemic due to the Omicron variant. The case toll due to the Omicron wave is likely to outnumber the earlier Delta wave, but the death toll is proportionately lower. Vaccination campaigns for the booster dose should be expedited to prevent severe illnesses and deaths in the population.

Effect of Surface Porosity on SARS-CoV-2 Fomite Infectivity

Previous reports indicated the low stability of severe actute respiratory syndrome coronovirus 2 (SARS-CoV-2) on various porous surfaces, but the role of porosity was unclear because there was no direct comparison between porous and nonporous solids of the same chemistry. Through comparing pairs of solids with very similar chemistry, we find that porosity is important: porous glass has a much lower infectivity than nonporous glass. However, porosity is not sufficient to lower infectivity; permeability, which is the ability of a liquid to move through a material, is the important parameter. We show this by comparing a pair of porous CuO coatings where the pores are accessible in one case and inaccessible in the other case. When the pores are inaccessible, the infectivity remains similar to that for nonporous solids. Thus, for both glass and CuO, it is the access to porosity that decreases the infectivity of extracted liquid droplets. Having established the importance of permeability, there is the open question of the mechanism of changing the infectivity of SARS-CoV-2. Several hypotheses are possible, such as increasing the difficulty of extracting the virus from the solid, changing the drying time, increasing the surface area of active ingredient, etc. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) measurements show that less viral DNA is extracted from a permeable surface, suggesting that the virus becomes trapped in the pores. Finally, we consider the effect of drying. We show that permeability and the water contact angle on the solid have effects on the drying time of a contaminated droplet, which may in turn affect infectivity.

Numerical Flow Simulation on the Virus Spread of SARS-CoV-2 Due to Airborne Transmission in a Classroom

In order to continue using highly frequented rooms such as classrooms, seminar rooms, offices, etc., any SARS-CoV-2 virus concentration that may be present must be kept low or reduced through suitable ventilation measures. In this work, computational fluid dynamics (CFD) is used to develop a virtual simulation model for calculating and analysing the viral load due to airborne transmission in indoor environments aiming to provide a temporally and spatially-resolved risk assessment with explicit relation to the infectivity of SARS-CoV-2. In this work, the first results of the model and method are presented. In particular, the work focuses on a critical area of the education infrastructure that has suffered severely from the pandemic: classrooms. In two representative classroom scenarios (teaching and examination), the duration of stay for low risk of infection is investigated at different positions in the rooms for the case that one infectious person is present. The results qualitatively agree well with a documented outbreak in an elementary school but also show, in comparisons with other published data, how sensitive the assessment of the infection risk is to the amount of virus emitted on the individual amount of virus required for infection, as well as on the supply air volume. In this regard, the developed simulation model can be used as a useful virtual assessment for a detailed seat-related overview of the risk of infection, which is a significant advantage over established analytical models.

Risk assessment and implementation of risk reduction measures is not associated with increased transmission of SARS-CoV-2 compared with standard isolation at professional golf events

Objectives

The purpose of this prospective study was to report incidence and transmission of SARS-CoV-2, among professional golfers and essential support staff undergoing risk assessment and enhanced risk reduction measures when considered a close contact as opposed to standard isolation while competing on the DP World Tour during the 2021 season.

Methods

This prospective cohort study included all players and essential support staff participating in 26 DP World Tour events from 18 April 2021 to 21 November 2021. High-risk contacts were isolated for 10 days. Moderate-risk contacts received education regarding enhanced medical surveillance, had daily rapid antigen testing for 5 days, with reverse transcriptase-polymerase chain reaction (RT-PCR) tesing on day 5, mandated mask use and access to outside space for work purposes only. Low-risk contacts typically received rapid antigen testing every 48 hours and RT-PCR testing on day 5.

Results

The total study cohort compromised 13 394 person-weeks of exposure. There were a total of 30 positive cases over the study period. Eleven contacts were stratified as 'high risk'. Two of these subsequently tested positive for SARS-CoV-2. There were 79 moderate-risk contact and 73 low-risk contacts. One moderate-risk contact subsequently tested positive for SARS-CoV-2 but did not transmit the virus. All other contacts, remained negative and asymptomatic to the end of the tournament week.

Conclusions

A risk assessment and risk reduction-based approach to contact tracing was safe in this professional golf event setting when Alpha and Delta were the predominant variants. It enabled professional golfers and essential support staff to work.

SARS-CoV-2 Droplet and Airborne Transmission Heterogeneity

The spread dynamics of the SARS-CoV-2 virus have not yet been fully understood after two years of the pandemic. The virus's global spread represented a unique scenario for advancing infectious disease research. Consequently, mechanistic epidemiological theories were quickly dismissed, and more attention was paid to other approaches that considered heterogeneity in the spread. One of the most critical advances in aerial pathogens transmission was the global acceptance of the airborne model, where the airway is presented as the epicenter of the spread of the disease. Although the aerodynamics and persistence of the SARS-CoV-2 virus in the air have been extensively studied, the actual probability of contagion is still unknown. In this work, the individual heterogeneity in the transmission of 22 patients infected with COVID-19 was analyzed by close contact (cough samples) and air (environmental samples). Viral RNA was detected in 2/19 cough samples from patient subgroups, with a mean Ct (Cycle Threshold in Quantitative Polymerase Chain Reaction analysis) of 25.7 ± 7.0. Nevertheless, viral RNA was only detected in air samples from 1/8 patients, with an average Ct of 25.0 ± 4.0. Viral load in cough samples ranged from 7.3 × 105 to 8.7 × 108 copies/mL among patients, while concentrations between 1.1-4.8 copies/m3 were found in air, consistent with other reports in the literature. In patients undergoing follow-up, no viral load was found (neither in coughs nor in the air) after the third day of symptoms, which could help define quarantine periods in infected individuals. In addition, it was found that the patient's Ct should not be considered an indicator of infectiousness, since it could not be correlated with the viral load disseminated. The results of this work are in line with proposed hypotheses of superspreaders, which can attribute part of the heterogeneity of the spread to the oversized emission of a small percentage of infected people.

Adsorption of SARS CoV-2 spike proteins on various functionalized surfaces correlates with the high transmissibility of Delta and Omicron variants

The SARS-CoV-2 virus emerged at the end of 2019 and rapidly developed several mutated variants, specifically the Delta and Omicron, which demonstrate higher transmissibility and escalating infection cases worldwide. The dominant transmission pathway of this virus is via human-to-human contact and aerosols which once inhaled interact with the mucosal tissue, but another possible route is through contact with surfaces contaminated with SARS-CoV-2, often exhibiting long-term survival. Here we compare the adsorption capacities of the S1 and S2 subunits of the spike (S) protein from the original variant to that of the S1 subunit from the Delta and Omicron variants on self-assembled monolayers by Quartz Crystal ​Microbalance. The results clearly show a significant difference in adsorption capacity between the different variants, as well as between the S1 and S2 subunits. Overall, our study demonstrates that while the Omicron variant is able to adsorb much more successfully than the Delta, both variants show enhanced adsorption capacity than that of the original strain. We also examined the influence of pH conditions on the adsorption ability of the S1 subunit and found that adsorption was strongest at pH 7.4, which is the physiological pH. The main conclusion of this study is that there is a strong correlation between the adsorption capacity and the transmissibility of the various SARS-CoV-2 variants.

[Infection prevention and control for COVID-19 in healthcare settings]

In healthcare facilities, the initial response to emerging and reemerging infectious diseases, including COVID-19, requires systematic management. The first step is to establish an initial risk assessment and subsequent response flow, using a combination of triage and clinical examination for patients. Screening tests are performed for the early diagnosis of asymptomatic patients who are judged to be at low risk in the initial assessment. However, regardless of the test results, subsequent patient care should be taken cautiously to avoid inadequate initial evaluation at the time of admission, follow-up of symptoms and infection control measures after admission. The basic principle is standard precautions, with particular emphasis on compliance with hand hygiene. Universal masking for preventing transmission from asymptomatic/pre-symptomatic patients and reducing droplet emission and inhalation become the new essential precaution. For suspected/confirmed patients with COVID-19, surgical mask or N95 mask, gloves, gown, eye protection, and cap are basically used. The policy for personal protective equipment is made based on the medical environment of each facility. A negative pressure room is not always required but should be considered in high-risk environments, if possible. While the risk of transmission from the surface environment in a standard healthcare delivery system is limited, a continuous review of the facility environment is expected, considering the importance of ventilation.