Characterization of Aerosols Generated During Patient Care Activities

Airborne transmission of severe acute respiratory syndrome coronavirus-2 to healthcare workers: a narrative review

Healthcare workers are at risk of infection during the severe acute respiratory syndrome coronavirus‐2 pandemic. International guidance suggests direct droplet transmission is likely and airborne transmission occurs only with aerosol‐generating procedures. Recommendations determining infection control measures to ensure healthcare worker safety follow these presumptions. Three mechanisms have been described for the production of smaller sized respiratory particles (‘aerosols’) that, if inhaled, can deposit in the distal airways. These include: laryngeal activity such as talking and coughing; high velocity gas flow; and cyclical opening and closure of terminal airways. Sneezing and coughing are effective aerosol generators, but all forms of expiration produce particles across a range of sizes. The 5‐μm diameter threshold used to differentiate droplet from airborne is an over‐simplification of multiple complex, poorly understood biological and physical variables. The evidence defining aerosol‐generating procedures comes largely from low‐quality case and cohort studies where the exact mode of transmission is unknown as aerosol production was never quantified. We propose that transmission is associated with time in proximity to severe acute respiratory syndrome coronavirus‐1 patients with respiratory symptoms, rather than the procedures per se. There is no proven relation between any aerosol‐generating procedure with airborne viral content with the exception of bronchoscopy and suctioning. The mechanism for severe acute respiratory syndrome coronavirus‐2 transmission is unknown but the evidence suggestive of airborne spread is growing. We speculate that infected patients who cough, have high work of breathing, increased closing capacity and altered respiratory tract lining fluid will be significant producers of pathogenic aerosols. We suggest several aerosol‐generating procedures may in fact result in less pathogen aerosolisation than a dyspnoeic and coughing patient. Healthcare workers should appraise the current evidence regarding transmission and apply this to the local infection prevalence. Measures to mitigate airborne transmission should be employed at times of risk. However, the mechanisms and risk factors for transmission are largely unconfirmed. Whilst awaiting robust evidence, a precautionary approach should be considered to assure healthcare worker safety.

Respiratory viruses in the patient environment

OBJECTIVE

To characterize the presence and magnitude of viruses in the air and on surfaces in the rooms of hospitalized patients with respiratory viral infections, and to explore the association between care activities and viral contamination.

DESIGN

Prospective observational study.

SETTING

Acute-care academic hospital.

PARTICIPANTS

In total, 52 adult patients with a positive respiratory viral infection test within 3 days of observation participated. Healthcare workers (HCWs) were recruited in staff meetings and at the time of patient care, and 23 wore personal air-sampling devices.

METHODS

Viruses were measured in the air at a fixed location and in the personal breathing zone of HCWs. Predetermined environmental surfaces were sampled using premoistened Copan swabs at the beginning and at the end of the 3-hour observation period. Preamplification and quantitative real-time PCR methods were used to quantify viral pathogens.

RESULTS

Overall, 43% of stationary and 22% of personal air samples were positive for virus. Positive stationary air samples were associated with ≥5 HCW encounters during the observation period (odds ratio [OR], 5.3; 95% confidence interval [CI], 1.2-37.8). Viruses were frequently detected on all of the surfaces sampled. Virus concentrations on the IV pole hanger and telephone were positively correlated with the number of contacts made by HCWs on those surfaces. The distributions of influenza, rhinoviruses, and other viruses in the environment were similar.

CONCLUSIONS

Healthcare workers are at risk of contracting respiratory virus infections when delivering routine care for patients infected with the viruses, and they are at risk of disseminating virus because they touch virus-contaminated fomites.

Lack of Tularemia Among Health Care Providers With Close Contact With Infected Patients-A Case Series

Francisella tularensis has a low infectious dose and can infect laboratory staff handling clinical specimens. The risk to health care providers exposed during patient care is poorly defined. We describe 9 examples of health care providers who did not develop tularemia after significant exposures to infected patients.

Potential for occupational exposures to pathogens during bronchoscopy procedures

Bronchoscopy is classified as an aerosol-generating procedure, but it is unclear what drives the elevated infection risk observed among healthcare personnel performing the procedure. The objective of this study was to characterize pathways through which bronchoscopists may be exposed to infectious agents during bronchoscopy procedures. Aerosol number concentrations (0.2-1 µm aerodynamic diameter) were measured using a P-Trak Ultrafine Particle Counter 8525 and mass concentrations (<10 µm) were measured using a SidePak Personal Aerosol Monitor AM510 near the head of patients during bronchoscopy procedures. Procedure pathway, number of patient coughs, number of suctioning events, number of contacts with different surfaces by the pulmonologist, and the use and doffing of personal protective equipment were recorded by the investigator on a specially designed form. Any pulmonologist performing a bronchoscopy procedure was eligible to participate. A total of 18 procedures were observed. Mean particle number and mass concentrations were not elevated during procedures relative to those measured before or after the procedure, on average, but the concentrations were highly variable, exhibiting high levels periodically. Patients frequently coughed during procedures (median 65 coughs, range: 0-565 coughs), and suctioning was commonly performed (median 6.5 suctioning events, range: 0-42). In all procedures, pulmonologists contacted the patient (mean 22.3 contacts, range: 1-48), bronchoscope (mean 19.4 contacts, range: 1-46), and at least one environmental surface (mean 31.2 contacts, range: 3-62). In the majority of procedures, the participant contacted his or her body or personal protective equipment (PPE), with a mean of 17.3 contacts (range: 4-48). More often than not, the observed PPE doffing practices differed from those recommended. Bronchoscopy procedures were associated with short-term increased ultrafine or respirable aerosol concentrations, and there were opportunities for contact transmission.

Monogenic, polygenic, and oligogenic familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia has long been considered a monogenic disorder. However, recent advances in genetic analyses have revealed various forms of this disorder, including polygenic and oligogenic familial hypercholesterolemia. We review the current understanding of the genetic background of this disease.

RECENT FINDINGS

Mutations in multiple alleles responsible for low-density lipoprotein regulation could contribute to the development of familial hypercholesterolemia, especially among patients with mutation-negative familial hypercholesterolemia. In oligogenic familial hypercholesterolemia, multiple rare genetic variations contributed to more severe familial hypercholesterolemia.

SUMMARY

Familial hypercholesterolemia is a relatively common 'genetic' disorder associated with an extremely high risk of developing coronary artery disease. In addition to monogenic familial hypercholesterolemia, different types of familial hypercholesterolemia, including polygenic and oligogenic familial hypercholesterolemia, exist and have varying degrees of severity. Clinical and genetic assessments for familial hypercholesterolemia and clinical risk stratifications should be performed for accurate diagnosis, as should cascade screening and risk stratification for the offspring of affected patients.

Environmental and Personal Protective Equipment Contamination during Simulated Healthcare Activities

Providing care to patients with an infectious disease can result in the exposure of healthcare workers (HCWs) to pathogen-containing bodily fluids. We performed a series of experiments to characterize the magnitude of environmental contamination—in air, on surfaces and on participants—associated with seven common healthcare activities. The seven activities studied were bathing, central venous access, intravenous access, intubation, physical examination, suctioning and vital signs assessment. HCWs with experience in one or more activities were recruited to participate and performed one to two activities in the laboratory using task trainers that contained or were contaminated with fluorescein-containing simulated bodily fluid. Fluorescein was quantitatively measured in the air and on seven environmental surfaces. Fluorescein was quantitatively and qualitatively measured on the personal protective equipment (PPE) worn by participants. A total of 39 participants performed 74 experiments, involving 10–12 experimental trials for each healthcare activity. Healthcare activities resulted in diverse patterns and levels of contamination in the environment and on PPE that are consistent with the nature of the activity. Glove and gown contamination were ubiquitous, affirming the value of wearing these pieces of PPE to protect HCW’s clothing and skin. Though intubation and suctioning are considered aerosol-generating procedures, fluorescein was detected less frequently in air and at lower levels on face shields and facemasks than other activities, which suggests that the definition of aerosol-generating procedure may need to be revised. Face shields may protect the face and facemask from splashes and sprays of bodily fluids and should be used for more healthcare activities.

Recognition of aerosol transmission of infectious agents: a commentary

Although short-range large-droplet transmission is possible for most respiratory infectious agents, deciding on whether the same agent is also airborne has a potentially huge impact on the types (and costs) of infection control interventions that are required.The concept and definition of aerosols is also discussed, as is the concept of large droplet transmission, and airborne transmission which is meant by most authors to be synonymous with aerosol transmission, although some use the term to mean either large droplet or aerosol transmission.However, these terms are often used confusingly when discussing specific infection control interventions for individual pathogens that are accepted to be mostly transmitted by the airborne (aerosol) route (e.g. tuberculosis, measles and chickenpox). It is therefore important to clarify such terminology, where a particular intervention, like the type of personal protective equipment (PPE) to be used, is deemed adequate to intervene for this potential mode of transmission, i.e. at an N95 rather than surgical mask level requirement.With this in mind, this review considers the commonly used term of 'aerosol transmission' in the context of some infectious agents that are well-recognized to be transmissible via the airborne route. It also discusses other agents, like influenza virus, where the potential for airborne transmission is much more dependent on various host, viral and environmental factors, and where its potential for aerosol transmission may be underestimated.

Recognition of aerosol transmission of infectious agents: a commentary

Although short-range large-droplet transmission is possible for most respiratory infectious agents, deciding on whether the same agent is also airborne has a potentially huge impact on the types (and costs) of infection control interventions that are required.The concept and definition of aerosols is also discussed, as is the concept of large droplet transmission, and airborne transmission which is meant by most authors to be synonymous with aerosol transmission, although some use the term to mean either large droplet or aerosol transmission.However, these terms are often used confusingly when discussing specific infection control interventions for individual pathogens that are accepted to be mostly transmitted by the airborne (aerosol) route (e.g. tuberculosis, measles and chickenpox). It is therefore important to clarify such terminology, where a particular intervention, like the type of personal protective equipment (PPE) to be used, is deemed adequate to intervene for this potential mode of transmission, i.e. at an N95 rather than surgical mask level requirement.With this in mind, this review considers the commonly used term of 'aerosol transmission' in the context of some infectious agents that are well-recognized to be transmissible via the airborne route. It also discusses other agents, like influenza virus, where the potential for airborne transmission is much more dependent on various host, viral and environmental factors, and where its potential for aerosol transmission may be underestimated.

Environmental colonization and onward clonal transmission of carbapenem-resistant Acinetobacter baumannii (CRAB) in a medical intensive care unit: the case for environmental hygiene

Background

In May 2015, we noticed an increase in carbapenem-resistant Acinetobacter baumannii (CRAB) infections in the Medical Intensive Care Unit (MICU). To investigate this, we studied the extent of environmental contamination and subsequent onward clonal transmission of CRAB.

Methods

We conducted a one-day point prevalence screening (PPS) of the patients and environment in the MICU. We screened patients using endotracheal tube aspirates and swabs from nares, axillae, groin, rectum, wounds, and exit sites of drains. We collected environmental samples from patients’ rooms and environment outside the patients’ rooms. CRAB isolates from the PPS and clinical samples over the subsequent one month were studied for genetic relatedness by whole genome sequencing (WGS).

Results

We collected 34 samples from seven patients and 244 samples from the environment. On the day of PPS, we identified 8 CRAB carriers: 3 who screened positive and 5 previously known clinical infections. We detected environmental contamination in nearly two-thirds of the rooms housing patients with CRAB. WGS demonstrated genetic clustering of isolates within rooms but not across rooms. We analysed 4 CRAB isolates from clinical samples following the PPS. One genetically-related CRAB was identified in the respiratory sample of a patient with nosocomial pneumonia, who was admitted to the MICU five days after the PPS.

Conclusion

The extensive environmental colonization of CRAB by patients highlights the importance of environmental hygiene. The transmission dynamics of CRAB needs further investigation.

Near-Patient Sampling to Assist Infection Control-A Case Report and Discussion

Air sampling as an aid to infection control is still in an experimental stage, as there is no consensus about which air samplers and pathogen detection methods should be used, and what thresholds of specific pathogens in specific exposed populations (staff, patients, or visitors) constitutes a true clinical risk. This case report used a button sampler, worn or held by staff or left free-standing in a fixed location, for environmental sampling around a child who was chronically infected by a respiratory adenovirus, to determine whether there was any risk of secondary adenovirus infection to the staff managing the patient. Despite multiple air samples taken on difference days, coinciding with high levels of adenovirus detectable in the child's nasopharyngeal aspirates (NPAs), none of the air samples contained any detectable adenovirus DNA using a clinically validated diagnostic polymerase chain reaction (PCR) assay. Although highly sensitive, in-house PCR assays have been developed to detect airborne pathogen RNA/DNA, it is still unclear what level of specific pathogen RNA/DNA constitutes a true clinical risk. In this case, the absence of detectable airborne adenovirus DNA using a conventional diagnostic assay removed the requirement for staff to wear surgical masks and face visors when they entered the child's room. No subsequent staff infections or outbreaks of adenovirus have so far been identified.