SARS-CoV-2 air sampling: A systematic review on the methodologies for detection and infectivity

This systematic review aims to present an overview of the current aerosol sampling methods (and equipment) being used to investigate the presence of SARS-CoV-2 in the air, along with the main parameters reported in the studies that are essential to analyze the advantages and disadvantages of each method and perspectives for future research regarding this mode of transmission. A systematic literature review was performed on PubMed/MEDLINE, Web of Science, and Scopus to assess the current air sampling methodologies being applied to SARS-CoV-2. Most of the studies took place in indoor environments and healthcare settings and included air and environmental sampling. The collection mechanisms used were impinger, cyclone, impactor, filters, water-based condensation, and passive sampling. Most of the reviewed studies used RT-PCR to test the presence of SARS-CoV-2 RNA in the collected samples. SARS-CoV-2 RNA was detected with all collection mechanisms. From the studies detecting the presence of SARS-CoV-2 RNA, fourteen assessed infectivity. Five studies detected viable viruses using impactor, water-based condensation, and cyclone collection mechanisms. There is a need for a standardized protocol for sampling SARS-CoV-2 in air, which should also account for other influencing parameters, including air exchange ratio in the room sampled, relative humidity, temperature, and lighting conditions.This work was financially supported by: LA/P/0045/2020 (ALiCE) and UIDB/00511/2020–UIDP/00511/2020 (LEPABE) funded by national funds through FCT/MCTES (PIDDAC); Project PTDC/EAM-AMB/32391/2017, funded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. Priscilla G. Silva thanks the Portuguese Foundation for Science and Technology – FCT for the financial support of her PhD work (2020.07806.BD, CRM: 0026504) contract through the DOCTORATES 4 COVID-19 program. Sofia I.V. Sousa thanks the Portuguese Foundation for Science and Technology (FCT) for the financial support of her work contract through the Scientific Employment Stimulus—Individual Call—CEECIND/02477/2017

Airborne spread of infectious SARS-CoV-2: Moving forward using lessons from SARS-CoV and MERS-CoV

Background: Although an increasing body of data reports the detection of SARS-CoV-2 RNA in air, this does not correlate to the presence of infectious viruses, thus not evaluating the risk for airborne COVID-19. Hence there is a marked knowledge gap that requires urgent attention. Therefore, in this systematic review, viability/stability of airborne SARS-CoV-2, SARS-CoV and MERS-CoV viruses is discussed. Methods: A systematic literature review was performed on PubMed/MEDLINE, Web of Science and Scopus to assess the stability and viability of SARS-CoV, MERS-CoV and SARS-CoV-2 on air samples. Results and discussion: The initial search identified 27 articles. Following screening of titles and abstracts and removing duplicates, 11 articles were considered relevant. Temperatures ranging from 20 °C to 25 °C and relative humidity ranging from 40% to 50% were reported to have a protective effect on viral viability for airborne SARS-CoV and MERS-CoV. As no data is yet available on the conditions influencing viability for airborne SARS-CoV-2, and given the genetic similarity to SARS-CoV and MERS-CoV, one could extrapolate that the same conditions would apply. Nonetheless, the effect of these conditions seems to be residual considering the increasing number of cases in the south of USA, Brazil and India, where high temperatures and humidities have been observed. Conclusion: Higher temperatures and high relative humidity can have a modest effect on SARS-CoV-2 viability in the environment, as reported in previous studies to this date. However, these studies are experimental, and do not support the fact that the virus has efficiently spread in the tropical regions of the globe, with other transmission routes such as the contact and droplet ones probably being responsible for the majority of cases reported in these regions, along with other factors such as human mobility patterns and contact rates. Further studies are needed to investigate the extent of aerosol transmission of SARS-CoV-2 as this would have important implications for public health and infection-control policies.This work was financially supported by Base Funding - UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy – LEPABE - funded by national funds through the FCT/MCTES (PIDDAC). This work was also financed by RESEARCH4COVID program under projects SARSBLOODsafe (ref 021), Cdots Biosensing COVID19 (ref 041) and fta4COVID19 (ref 598) funded by the Portuguese Foundation for Science and Technology (FCT); Sofia I.V. Sousa thanks FCT for the financial support of her work contract through the Scientific Employment Stimulus - Individual Call - CEECIND/02477/2017; Priscilla Gomes da Silva thanks FCT for the financial support of her PhD work (2020.07806.BD) contract through the DOCTORATES 4 COVID-19 program

Evidence of Air and Surface Contamination with SARS-CoV-2 in a Major Hospital in Portugal

As the third wave of the COVID-19 pandemic hit Portugal, it forced the country to reintro-duce lockdown measures due to hospitals reaching their full capacities. Under these circumstances, environmental contamination by SARS-CoV-2 in different areas of one of Portugal’s major Hospitals was assessed between 21 January and 11 February 2021. Air samples (n = 44) were collected from eleven different areas of the Hospital (four COVID-19 and seven non-COVID-19 areas) using Coriolis® µ and Coriolis® Compact cyclone air sampling devices. Surface sampling was also performed (n = 17) on four areas (one COVID-19 and three non-COVID-19 areas). RNA extraction followed by a one-step RT-qPCR adapted for quantitative purposes were performed. Of the 44 air samples, two were positive for SARS-CoV-2 RNA (6575 copies/m3 and 6662.5 copies/m3, respectively). Of the 17 surface samples, three were positive for SARS-CoV-2 RNA (200.6 copies/cm2, 179.2 copies/cm2, and 201.7 copies/cm2, respectively). SARS-CoV-2 environmental contamination was found both in air and on surfaces in both COVID-19 and non-COVID-19 areas. Moreover, our results suggest that longer collection sessions are needed to detect point contaminations. This reinforces the need to remain cautious at all times, not only when in close contact with infected individuals. Hand hygiene and other standard transmission-prevention guidelines should be continuously followed to avoid nosocomial COVID-19. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding text 1: Acknowledgments: Priscilla Gomes da Silva thanks the Portuguese Foundation for Science and Technology–FCT for the financial support of her PhD work (2020.07806.BD, CRM: 0026504) contract through the DOCTORATES 4 COVID-19 program. Sofia I.V. Sousa thanks the Portuguese Foundation for Science and Technology (FCT) for the financial support of her work contract through the Scientific Employment Stimulus-Individual Call-CEECIND/02477/2017.; Funding text 2: Funding: This work was financially supported by Base Funding-UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy–LEPABE—funded by national funds through the FCT/MCTES (PIDDAC)

Electric field driven addressing of ATPS droplets in microfluidic chips

Referujeme o možnosti ovlivňovat pohyb kapek (adresování kapek) pomocí stejnosměrného elektrického pole v systému dvoufázového vodného roztoku (ATPS). Byly zkoumány tři systémy ATPS typu polyetylenglykol/sůl, jmenovitě polyetylenglykol/fosfát, polyetylenglykol/síran a polyetylenglykol/uhličitan. Série pokusů s adresováním a slučováním kapek v mikrofluidním čipu ukázaly, že stejnosměrné elektrické pole může být užitečným nástrojem pro chytrou manipulaci kapek v systémech polyetylenglykol/sůl.The possibility of controlled droplet motion (droplet addressing) mediated by DC electric field in aqueous two-phase systems (ATPS) is here reported for the first time. Three ATPS of polyethylene glycol (PEG)/salt type, namely PEG/phosphate, EG/sulphate, and PEG/carbonate, were selected for this study. We observed fast motion of salty droplets dispersed in PEG continuous phase induced by electric field of relative low strength. Hence, three fluidic systems with separated electrode chambers for the evaluation of electrophoretic mobilities and for addressing experiments were fabricated. Electrophoretic mobilities of salty droplets always exceeded the value of 1 × 10−7 m2V−1s−1, which is about by one magnitude higher value than those typically measured in water–oil droplet systems. The electrophoretic mobilities in systems with free surface are the same or even smaller than in closed microfluidic structures, which is accounted mainly to the fact that a significant part of salty droplets is exposed to air and does not contribute to droplet forcing. Series of addressing and merging experiments in a microfluidic chip shows that DC electric field can be used as a powerful tool for smart manipulation of droplets in microfluidic systems with PEG/salt ATPS