Quantitative modeling of the impact of facemasks and associated leakage on the airborne transmission of SARS-CoV-2

FIFA Arab Cup tournament with full capacity of spectators during the COVID-19 pandemic: a cross-sectional study

BACKGROUND

We sought to assess the risk of COVID-19 and seasonal flu including respiratory syncytial (RSV) and influenza viruses during the FIFA Arab Cup 2021 in Qatar with full capacity of spectators. We also, evaluated the post-event attitude toward resumption of mass football events.

METHODS

This was a cross-sectional study in which spectators (age ≥ 18 years) were invited for reverse-transcription PCR testing for COVID-19 and seasonal flu. At the same time, between 7 and 14 days after the event, the participants completed a self-administered questionnaire regarding their concerns during the tournament.

RESULTS

The tournament included 16 international football teams from the Arab countries. As per the study protocol, 10,000 spectators were approached and 6,475 participated. Among the participants, 4,195 (65.1%), 2,253 (34.9%) and 27 (0.4%) were vaccinated with 2 doses, vaccinated with 3 doses, and recovered from SARS-Cov-2 infection, respectively. There were 61 (0.9%), 41(0.6%) and 11(0.2%) participants who tested positive for COVID-19, RSV and influenza (A/B), respectively. The average cycle threshold (Ct) value for COVID-19 positive cases was 26.1±7.3. Among those who were electronically approached, 6,102 completed the survey whereas 373 had incomplete survey. Overall, 2069 (33.9%) participants reported symptoms that theoretically could be related to COVID-19, of them 39 had positive PCR test (1.9%). Spectators (94.3%) were optimistic about returning sport events to the pre-pandemic status.

CONCLUSIONS

There was no significant increase in the daily COVID-19 cases during FIFA Arab Cup 2021 with a full capacity of spectators. Therefore, upcoming mass football events can be held safely.

Diagnostic performance of respirators for collection and detection of SARS-CoV-2

Respirators, called as face mask, have been used to protect the wearer from the outside harmful air environment and prevent any virus from being released to neighbors from potentially infected exhaled breath. The antiviral effectiveness of respirators has not only been researched scientifically, but has also become a global issue due to society's obligation to wear respirators. In this paper, we report the results of a study on the collection and detection of viruses contained in exhaled breath using respirators. The inner electrostatic filter was carefully selected for virus collection because it does not come in direct contact with either human skin or the external environment. In the study of a healthy control group, it was confirmed that a large amount of DNA and biomolecules such as exosomes were collected from the respirator exposed to exhalation, and the amount of collection increased in proportion to the wearing time. We conducted experiments using a total of 72 paired samples with nasopharyngeal swabs and respirator samples. Out of these samples, fifty tested positive for SARS-CoV-2 and twenty-two tested negative. The PCR results of the NPS and respirator samples showed a high level of agreement, with a positive percent agreement of ≥ 90% and a negative percent agreement of ≥ 99%. Furthermore, there was a notable level of concordance between RCA-flow tests and PCR when examining the respirator samples. These results suggest that this is a non-invasive, quick and easy method of collecting samples from subjects using a respirator, which can significantly reduce the hassle of waiting at airports or public places and concerns about cross-contamination. Furthermore, we expect miniaturized technologies to integrate PCR detection into respirators in the near future.

SARS-CoV-2 infection in patients with or at risk for venereal infections: Incidence and associated factors in a sexual health clinic

BACKGROUND AND OBJECTIVE

SARS-CoV-2 is more easily spread by close contact, which is inherent to sexual intercourse. People with, or at risk for, sexually transmitted infections (STIs) may therefore have higher rates of COVID-19. The aim of this study was to estimate SARS-CoV-2 antibody seroprevalence in people seen at a dedicated STI clinic, compare our findings to the estimated seroprevalence in the local general population, and study factors associated with SARS-CoV-2 infection in this setting.

MATERIAL AND METHODS

Cross-sectional observational study including consecutive patients older than 18 years of age who had not yet been vaccinated against COVID-19 and who underwent examination or screening at a dedicated municipal STI clinic in March and April 2021. We ordered rapid SARS-CoV-2 serology and collected information on demographic, social, and sexual variables, STI diagnoses, and history of symptoms compatible with SARS-CoV-2 infection.

RESULTS

We studied 512 patients (37% women). Fourteen (24.2%) had a positive SARS-CoV-2 test. Variables associated with positivity were use of FFP2 masks (odds ratio 0.50) and a higher-than-average number of sexual partners (odds ratio 1.80). Use of FFP2 masks was not randomly distributed in this sample.

CONCLUSIONS

Sexually active members of the population in this study had a higher incidence of SARS-CoV-2 infection than the general population. The main route of infection in this group appears to be respiratory, linked to close contact during sexual encounters; sexual transmission of the virus is probably limited.

Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol

The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90%) and low (40%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.

Influence of face masks on the subjective impairment at different physical workloads

To quantify the subjective and cognitive impairment caused by wearing face masks at work, 20 men and 20 women (median age 47 years, range 19-65) were tested under different ergometer workloads while wearing surgical mask, community mask, FFP2 respirator or no mask in a randomized and partially double-blinded design. Masks were worn also at the workplace for four hours. Subjective impairment was recorded by questionnaires. Cognitive performance was tested before and after the workplace examination. Subjective feeling of heat, humidity, and difficult breathing increased with rising physical exertion and wearing time for all three mask types, most notably for FFP2. Even when blinded, participants with FFP2 reported difficult breathing already at rest. During physical exertion, individuals with low tolerance to discomfort reported significantly stronger impairment (OR 1.14, 95% CI 1.02-1.27). Regarding light work, older subjects (OR 0.95, 95% CI 0.92-0.98) and women (OR 0.84, 95% CI 0.72-0.99) showed significantly lower and atopic subjects stronger impairment (OR 1.16, 95% CI 1.06-1.27). No significant influence of mask wearing was detected on cognitive performance. Wearing a mask had no effect on cognitive performance, but led to discomfort which increased with physical exertion and wearing time. Individuals who tolerate discomfort poorly felt more impaired by wearing a mask during physical exertion.

Designing better cloth masks: The effect of fabric and attachment-style on discomfort

Cloth masks are a tool for controlling community transmission during pandemics, as well as during other outbreak situations. However, cloth masks vary in their designs, and the consequences of this variability for their effectiveness as source control have received little attention, particularly in terms of user discomfort and problematic mask-wearing behaviors. In the present studies, common design parameters of cloth masks were systematically varied to ascertain their effect(s) on the subjective discomfort and frequency of problematic mask-wearing behaviors, which detract from the effectiveness of cloth masks as source control. The type of fabric comprising a mask (flannel or twill made of 100% cotton) and the attachment-style of a mask (i.e., ear loops or fabric ties) were varied in adults (18 to 65 years) and children (ages 6 to 11 years). For adults, ear loops were less comfortable than ties (p = .035) and were associated with greater face- (p = .005) and mask-touching (p = .001). Children, however, found flannel masks to be more breathable than twill masks (p = .007) but touched their masks more frequently when wearing a mask made of flannel than twill (p = .033). Common design parameters of cloth masks not only affect user discomfort and behavior but do so differently in adults and children. To improve the effectiveness of cloth masks as source control, the present studies highlight the importance of measuring the effect(s) of design decisions on user discomfort and behavior in different populations.

Materials analysis and image-based modelling of transmissibility and strain behaviour in approved face mask microstructures

Comparisons are made between six different approved face masks concerning their particle transmissibility allied to mechanical properties. The latter involves material testing and stretch or strain behaviour under load. SEM and X-ray elemental analyses showed contrasting structures between random and ordered fibre orientations. These constitute the mask designs where transmissibility is to be minimised. Airflow velocity measurement enabled filtration to be measured between the different mask designs, from two to six layers of different fabrics in combination. SEM provided the fibre diameter and pore size of each mask layer, up to a maximum of six. Stretching each complete mask showed its elasticity and recovery behaviour on an energy basis. The energy conversion involved in mask straining involves areas enclosed within steady and cyclic load-extension plots. Thus, the work done in extending a mask and the energy recovered from its release identified a hysteresis associated with an irrecoverable permanent stretch to the mask fabric. Failure of individual layers, which occurred successively in extended stretch tests, appeared as a drop in a load-extension response. That change is associated with permanent damage to each mask and friction contact within the rearrangement of loose fibre weaves. Masks with the greatest number of layers reduced particle transmissibility. However, woven or ordered mask fabrics in two layers with different orientations provided comparable performance. Simulation of each mechanical response, velocity streamlining and fibre distribution within the mask layers are also presented.

A critical review on the role of leakages in the facemask protection against SARS-CoV-2 infection with consideration of vaccination and virus variants

The protection provided by facemasks has been extensively investigated since the beginning of the SARS-CoV-2 outbreak, focusing mostly on the filtration efficiency of filter media for filtering face pieces (FFP), surgical masks, and cloth masks. However, faceseal leakage is a major contributor to the number of potentially infectious airborne droplets entering the respiratory system of a susceptible individual. The identification of leaking spots and the quantification of leaking flows are crucial to estimate the protection provided by facemasks. This study presents a critical review on the measurement and calculation of facemask leakages and a quantitative analysis of their role in the risk of SARS-CoV-2 infection. It shows that the pairing between the mask dimensions and the wearer's face is essential to improve protection efficiency, especially for FFP2 masks, and summarizes the most common leaking spots at the interface between the mask and the wearer's face. Leakage is a crucial factor in the calculation of the protection provided by facemasks and outweighs the filtration performances. The fit factors measured among mask users were summarized for different types of face protection. The reviewed data were integrated into a computational model to compare the mitigation impact of facemasks with vaccination with consideration of new variants of SARS-CoV-2. Combining a high adoption rate of facemasks and a high vaccination rate is crucial to efficiently control the spread of highly infectious variants.

Collection and detection of SARS-CoV-2 in exhaled breath using face mask

Face masks are used to protect the wearer from harmful external air and to prevent transmission of viruses from air exhaled by potentially infected wearers to the surrounding people. In this study, we examined the potential utility of masks for collecting viruses contained in exhaled breath and detected the collected viruses via various molecular tests. Using KF94 masks, the inner electrostatic filter was selected for virus collection, and an RNA extraction protocol was developed for the face mask. Virus detection in worn mask samples was performed using PCR and rolling circle amplification (RCA) tests and four different target genes (N, E, RdRp, and ORF1ab genes). The present study confirmed that the mask sample tests showed positive SARS-CoV-2 results, similar to the PCR tests using nasopharyngeal swab samples. In addition, the quantity of nucleic acid collected in the masks linearly increased with wearing time. These results suggest that samples for SARS-CoV-2 tests can be collected in a noninvasive, quick, and easy method by simply submitting worn masks from subjects, which can significantly reduce the hassle of waiting at airports or public places and concerns about cross-infection. In addition, it is expected that miniaturization technology will integrate PCR assays on face masks in the near future, and mask-based self-diagnosis would play a significant role in resolving the pandemic situation.

Investigation of the Role of Face Shape on the Flow Dynamics and Effectiveness of Face Masks

Due to the COVID-19 pandemic, face masks have been used extensively in society. The effectiveness of face masks depends on their material, design, and fit. With much research being focused on quantifying the role of the material, the design and fit of masks have been an afterthought at most. Recent studies, on the other hand, have shown that the mask fit is a significant factor to consider when specifying the effectiveness of the face mask. Moreover, the fit is highly dependent on face topology. Differences in face types and anthropometrics lead to different face mask fit. Here, computational fluid dynamics simulations employing a novel model for porous membranes (i.e., masks) are used to study the leakage pattern of a cough through a face mask on different faces. The three faces studied (female, male, and child) are characteristic faces identified in a previous population study. The female face is observed to have the most leakage through the periphery of the mask, which results in the lowest fitted filtration efficiency of the three faces. The male and child faces had similar gap profiles, leakage and fitted filtration efficiencies. However, the flow of the three faces differs significantly. The effect of the porosity of the mask was also studied. While all faces showed the same general trend with changing porosity, the effect on the child’s face was more significant.

A Simple Method to Quantify Outward Leakage of Medical Face Masks and Barrier Face Coverings: Implication for the Overall Filtration Efficiency

Face masking proved essential to reduce transmission of COVID-19 and other respiratory infections in indoor environments, but standards and literature do not provide simple quantitative methods for quantifying air leakage at the face seal. This study reports an original method to quantify outward leakage and how wearing style impacts on leaks and filtration efficiency. The amount of air leakage was evaluated on four medical masks and four barrier face coverings, exploiting a theoretical model and an instrumented dummy head in a range of airflows between 30 and 160 L/min. The fraction of air leaking at the face seal of the medical masks and barrier face coverings ranged from 43% to 95% of exhaled air at 30 L/min and reduced to 10-85% at 160 L/min. Filter breathability was the main driver affecting both leak fraction and total filtration efficiency that varied from 5% to 53% and from 15% to 84% at 30 and 160 L/min, respectively. Minor changes were related to wearing style, supporting indications on the correct mask use. The fraction of air leaking from medical masks and barrier face coverings during exhalation is relevant and varies according to design and wearing style. The use of highly breathable filter materials reduces air leaks and improve total filtration efficiency.