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

Abstract

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.

Frequency, kinetics and determinants of viable SARS-CoV-2 in bioaerosols from ambulatory COVID-19 patients infected with the Beta, Delta or Omicron variants

“…The frequency of aerosol virus culturability was high at ~60%. This is in contrast to published studies using size fractionated air sampling methodologies that, although few in number, have been mostly unsuccessful at culturing virus from aerosols generated from patients with acute SARS-CoV-2 infection 9 , 20 – 22 (with two studies demonstrating culturable virus in a total of five COVID-19 cases) 16 , 17 This could potentially be explained by several factors including viral dehydration and destruction during collection and laboratory transport, viral destruction due to impact forces related to the method of collection (e.g. high velocity impingement systems), and viral retention in sampling equipment and tubing 9 .…”

“…However, whilst airborne transmission of SARS-CoV-2 by respiratory droplets over short distances (1 to 2 metres) is well accepted, longer distance airborne transmission by fine aerosols (particles <10 μm) that can directly inoculate the deeper lung, remains contentious for several reasons including that it is difficult to demonstrate directly. Furthermore, although SARS-CoV-2 has been detected in hospital-based and community air samples, size fractionation and viral culture were not performed in most of these investigations 6 – 9 . Factors that support aerosol-based transmission have been cogently summarised 10 and include demonstration of long-range transmission in quarantine hotels 11 , restaurants and choirs 12 , demonstration of nosocomial transmission with masks that were permissive to aerosols but not droplets spread 13 , identification of SARS-CoV-2 genomic material in building ducts and air conditioning systems, and in transmission ducted animal experiments 14 , 15 .…”

Research progress of severe acute respiratory syndrome coronavirus 2 on aerosol collection and detection

“…To improve our understanding of the mechanisms of airborne transmission of viruses, air sampling techniques to detect the presence of aerosol viruses, efficiently collect and maintain their activity, and determine their distribution in aerosol particles are necessary [13] . Several methods have been developed for sampling microbial aerosols, such as natural sedimentation [14] , solid impact [15] , liquid impact [16] , centrifugal, cyclone [17] and electrostatic adsorption [18] methods. These methods are classified as either active or passive sampling [ 19 , 20 ].…”

Detection of infectious SARS-CoV-2 in frozen aerosol samples collected from hospital rooms of patients with COVID-19

“…At the stage of the COVID-19 pandemic where vaccines have greatly contributed to limiting the severity of the disease and the pressure on health systems, surveillance methods allowing the assessment of community levels of SARS-CoV-2 remain essential to inform decisions about strategies to prevent COVID-19 transmission. Understanding virus emission rate and subsequent transmission of SARS-CoV-2 through the air via particles of different sizes, generally called droplets and aerosols, implies that we have well-defined methods to monitor indoor air [1] [2]. This is essential to better understand viral resistance to environmental stress, inform on the risks of acquisition in the community and occupational environments and appropriately evaluate virus mitigation methods in indoor settings.…”