Models of influenza transmission have focused on the ability of vaccination, antiviral therapy, and social distancing strategies to mitigate epidemics. Influenza transmission, however, may also be interrupted by hygiene interventions such as frequent hand washing and wearing masks or respirators. We apply a model of influenza disease transmission that incorporates hygiene and social distancing interventions. The model describes population mixing as a Poisson process, and the probability of infection upon contact between an infectious and susceptible person is parameterized by p. While social distancing interventions modify contact rates in the population, hygiene interventions modify p. Public health decision making involves tradeoffs, and we introduce an objective function that considers the direct costs of interventions and new infections to determine the optimum intervention type (social distancing versus hygiene intervention) and population compliance for epidemic mitigation. Significant simplifications have been made in these models. However, we demonstrate that the method is feasible, provides plausible results, and is sensitive to the selection of model parameters. Specifically, we show that the optimum combination of nonpharmaceutical interventions depends upon the probability of infection, intervention compliance, and duration of infectiousness. Means by which realism can be increased in the method are discussed.

National standards for surgical respirators and masks are written and enforced to protect healthcare workers from particles and microorganisms such as Severe Acute Respriatory Syndrome Coronavirus 2 (SARS-CoV-2). In addition to the ability to filter particles (e.g. filtration efficiency, FE), the standards address breathability (e.g. differential pressure), how well the mask seals to a worker's face (e.g. fit test), the level of protection from a fluid splash, and other factors. Standards used in the USA, European Union (EU), and China were compared with respect to testing methods and certification criteria. Although there are substantial similarities in standards for respirators, such as surgical N95, FFP2, and KN95 filtering facepiece respirators (FFRs), there are differences with respect to who performs that testing and fit-testing requirements that influence certification. There is greater variation in test methods between countries for surgical (USA) or medical (EU and China) masks than for FFRs. Surgical/medical masks can be certified to different levels of protection. The impact of the similarities and differences in testing methods and certification criteria on FFR and mask performance for protecting healthcare workers from SARS-CoV-2 are discussed, as well as the value of a new standard in the EU for testing fabrics for masks used by the public. Health and safety personnel in healthcare settings must understand the differences between standards so that they can select respirators and masks that provide appropriate protection for healthcare workers.

Background

Spurred by the Coronavirus infectious disease 2019 pandemic, aerosol containment devices (ACDs) were developed to capture infectious respiratory aerosols generated by patients at their source. Prior reviews indicated that such devices had low evidence of effectiveness, but did not address how ACDs should be evaluated, how well they should perform, nor have clearly defined performance standards. Towards developing design criteria for ACDs, two questions were posed: 1) What characteristics have guided the design of ACDs? 2) How have these characteristics been evaluated?

Methods

A scoping review was performed consistent with PRISMA guidelines. Data were extracted with respect to general study information, intended use of the device, device design characteristics and evaluation.

Results

Fifty-four articles were included. Evaluation was most commonly performed with respect to device aerosol containment (n = 31, 61%), with only 5 (9%), 3 (6%) and 8 (15%) formally assessing providing experience, patient experience and procedure impact, respectively. Nearly all of the studies that explored provider experience and procedure impact studied intubation. Few studies provided a priori performance criteria for any evaluation metric, or referenced any external guidelines by which to bench mark performance.

Conclusion

With respect to aerosol containment, ACDs should reduce exposure among HCP with the device compared with the absence of the device, and provide ≥90% reduction in respirable aerosols, equivalent in performance to N95 filtering facepiece respirators, if the goal is to reduce reliance on personal protective equipment. The ACD should not increase awkward or uncomfortable postures, or adversely impact biomechanics of the procedure itself as this could have implications for procedure outcomes. A variety of standardized instruments exist to assess the experience of patients and healthcare personnel. Integration of ACDs into routine clinical practice requires rigorous studies of aerosol containment and the user experience.