Sub-micron filtration can have positive impact on health


We have been discussing at our blog the solid air interface as a dynamic process vs. a static process.  Once particles – bacteria, virus, pollen, dirt, chemicals – that are on a surface the can be aerosolized with movement of people equipment or air. In part because of this, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends sub-micron filtration for hospitals and nursing homes. Below are links to some pieces that illustrate that need.

  • In a segment of a National Academy of Sciences, Engineering and Medicine meeting titled “Microbiomes of the Built Environment,” Donald Milton presents on the transfer of infectious disease via the air and some models to use in predicting the likelihood of these transfers in this YouTube piece: Donald Milton – Models: How to think about infections in the air? In his informative talk, Milton outlines how normal breathing, not just coughing and sneezing, contributes to the spread of respiratory viruses. He also notes that movements indoors cause several times the bioaerosol particles to be emitted, with the majority of those coming from the floor. Milton is Professor of Environmental Health, Applied Environmental Health (MIAEH) and Affiliate in Cell Biology and Molecular Genetics; Professor, Internal Medicine, University of Maryland School of Medicine.
  • At the same gathering, Perspectives on Microbial Interactions in Built Environments presented by Brent Stephens discusses how the indoor environment impact indoor air quality (IAQ). The bulk of the particles in coughs and sneezes are sub-micron sized, which supports ASHRAE’s recommendation for sub-micron filtration in hospitals and nursing homes. Stephens is an expert in the fate and transport of indoor pollutants, building energy and environmental measurements, HVAC filtration, human exposures to airborne pollutants, energy efficient buildings, energy and environmental policy.

Researchers seek to find accurate tools to detect infectious pathogens on aircraft

airlinesModern transportation offers conveniences unimaginable in previous eras, shrinking the world in ways few would have imagined not long ago. With the speed humans are able to travel long distances, it enables disease to hitch a ride and travel equally fast. In particular, aircraft have the potential to aid in the spread of disease. Because of that, we need to continually look at methods to control the transmission of disease and infection.

The potential for international airline passengers to transport infectious diseases from country to country is a reason for concern.  The 2003 severe acute respiratory syndrome (SARS) was found to be spread largely by air travelers, becoming a global epidemic that involved 774 fatalities and cost billions. Other viruses and even deliberate infection pose threats, too. Finding a tool to detect airborne infectious pathogens accurately and rapidly before passengers and crew leave the aircraft would be valuable.

Validation for CFD Prediction of Mass Transport in an Aircraft Passenger Cabin was published by the Federal Aviation Administration (FAA) in 2006. The abstract says: A joint project was established to validate computational fluid dynamics (CFD) as a quantitative methodology for prediction of the distribution of pathogens released into the environmental control system (ECS)-generated ventilation flowfield of an aircraft passenger cabin. Acquisition of the requisite experimental databases for three-dimensional velocity and contaminant distributions was accomplished in the FAA Civil Aerospace Medical Institute’s (CAMI’s) Aircraft Environmental Research Facility (AERF). The associated CFD simulations were conducted by the University of Tennessee CFD Laboratory staff, on the resident Beowulf PC cluster and/or the University of Tennessee Innovative Computing Laboratory SiNRG cluster, using both commercial and proprietary CFD computer codes. It is noted that “the CAMI AERF is an exceptionally valuable research facility to support research on the fate of pathogens introduced into aircraft cabin ventilation flowfields. The requirements are clearly delineated for the acquisition of quality velocity and mass transport experimental data to support CFD validation requirements. The astute use of CFD methodology can certainly generate precise design guidance for such experiments, effectively and efficiently reducing the size of the data matrix required to serve the validation requirement. The results of this steadily growing knowledge base will predict estimation of optimal opportunities for onboard sensor locations, hence will support associated hypotheses for examining potential damage mitigation strategies, should a cabin release event be detected.”

To understand contaminant transport and airflow patterns inside an aircraft cabin, previous researchers have used computational fluid dynamics (CFD) models to predict airflows with and without simulated passengers. An Analysis on the Detection of Biological Contaminants Aboard Aircraft considers “exhaled particles from regular breathing, coughing and sneezing. (Because) infectious airborne particles are typically under 20 microns, here we restrict our simulation and analysis to expellants with diameters under 20 microns. . . . Three scenarios of infectious “super spreader” passengers were investigated, consisting of states of extreme coughing, extreme sneezing, and regular breathing. Our principal finding was that the steady-state bacteria concentrations in aircraft would be high enough to be detected in the case where seven infectious passengers are exhaling under scenarios 1 (breathing and coughing) and 2 (breathing and sneezing), and where one infectious passenger is actively exhaling in scenario 2. Breathing alone failed to generate sufficient bacterial particles for detection, and none of the scenarios generated sufficient viral particles for viral detection to be feasible.” Related: State-of-the-Art Methods for Studying Air Distributions in Commercial Airliner Cabins.

Researchers Study How Microbes Travel Through the Air: Engineers and biologists are steering their efforts towards a new aerobiological modeling technique, one they think may assist farmers in the future by providing an early warning system for high-risk plant pathogens. It will also provide the basis for more effective management strategies to address the spread of infectious diseases affecting plants, domestic animals, and humans.

Previously at our blog, researchers at Technical University of Denmark studied the poop siphoned from airplane toilets from flights arriving from around the world: AIRLINE POOP STUDIED TO TRACK GLOBAL SPREAD OF AMR IN BACTERIAL PATHOGENS.

Dogs and rats offer unique tools to detect bacteria and disease

Photo credit: Darryl Dyck/The Canadian Press

The olfactory prowess of dogs is well-documented. They have been trained to sniff out everything from people to drugs, from land mines and bombs to potential seizures.  Not surprisingly, we now have one that is trained to track Clostridium difficile (C. diff), potentially providing a new and effective tool for infection control specialists. Meet world’s only superbug-sniffing dog, a spaniel named Angus who tracks C. diff at a Vancouver hospital tells the story of Angus, an English springer spaniel, who will be employed at Vancouver General Hospital as Canada’s first and only C. diff sleuth. The story, published at National Post and written by Pamela Fayerman, says “Angus uses his scent-tracking abilities to find toxins in the bacterial organisms that cause C. diff. infections which usually follow antibiotic use that alters the normal flora of the gut. He will work in hospital spaces that may prove to need more sanitizing, especially rooms that are being prepared for the next patient admission.” We applaud Vancouver General hospital executives for being receptive to this out-of-the-box thinking and keeping open minds in the continuing battle against hospital-associated infection.

And dogs aren’t the only animals being used in the effort. Rats, another creature with an extraordinary sense of smell and who were previously trained to detect landmines, are being repurposed to help with the fight against tuberculosis in Tanzania and Mozambique. Giant rats used to diagnose prisoners with tuberculosis in jails details why those with the program believe that their TB Detection Rat technology will prove itself as an effective mass-screening tool.


Shark micropattern shows it can put some teeth into antimicrobial efforts

The shark skin denticles (left) and the Sharklet micropattern. Sharklet Technologies, Inc. photo.

Biomimicry in the form of a shark micropattern could provide another option when it comes to persistently cleaning surfaces. Biomimicry uses elements of nature and replicates them in a laboratory for use in a variety of applications. A new technology has emerged using these manufactured micropatterns to prevent the accumulation of microbes on surfaces without toxic materials.

Copper and silver are used in hospitals because they are known to be cytotoxic to bacteria. The rub comes when some bacteria develop a resistance to the metals and continue to flourish on surfaces. Micropattern surfaces offer a new method to prevent bacterial colonization; the micropatterns make it difficult for bacteria to adhere and continue growing on the surface.  Because micropatterns are a physical/mechanical method of prevention, microbes do not develop a resistance to it.

Micropattern surfaces create an inhospitable surface and make it difficult for bacteria to colonize while at the same time inhibiting cell migration. Data shows the pattern reduces bacterial surface counts. Micropatterns inspired by shark skin represent a new approach to combating microbes without the use of toxic chemicals or overused antibiotics.

Surface micropattern limits bacterial contamination appears at PubMed Central and illustrates the potential this technology has. While future studies are necessary to determine the degree of impact, “the assays developed in this study mimic hospital environmental contamination events to demonstrate the performance of a MP to limit contamination under multiple conditions. Antimicrobial copper has been implemented in hospital room studies to evaluate its impact on nosocomial infections and a decrease in HAI rate was shown. Similar implementation of the MP has potential to reduce the incidence of healthcare-associated infections (HAIs).”

Surface Micropattern Resists Bacterial Contamination Transferred by Healthcare Practitioners at MedCrave tests and evaluates this technology in a clinical setting. It concludes that:

Bacterial transmission was reduced by a factor of 5.4 on the micropatterned surface compared to the corresponding unpatterned surface for the two locations that exhibited covariance. Importantly, reduced transmission occurred at all locations tested in this study but maximally at the defibrillator button by a factor of 13.8 times. Given that unpatterned surfaces allow more bacterial transmission, contributing to the spread of S. aureus on surfaces, there could be major benefits to patient safety in implementing this micropatterned surface that combats bacterial spread. Staphylococcus aureus was used in this study as a representative and common bacterial species, but the micropattern has been shown to reduce contamination of a wide range of microbial species in other studies. It is reasonable to expect the micropatterned surface to broadly reduce microbial transmission occurring on hospital surfaces. The Sharklet micropattern is a valuable option to combat transient surface contamination on high-touch surfaces, especially in hospitals and healthcare settings. This study demonstrates the ability of the micropattern to offer reduced transmission of S. aureus on hospital high-touch surfaces in simulated physician-patient environment interaction scenarios.

Studies show CDC’s droplet precaution guidance might fall short

sneezeThe Center for Disease Control (CDC) has provided guidance on droplet precaution that might need to be reconsidered. In the cloud: How coughs and sneezes float farther than you think is a study that uncovers the way coughs and sneezes stay airborne for long distances. Discussed at MIT News, the study specifically “finds that droplets 100 micrometers — or millionths of a meter — in diameter travel five times farther than previously estimated, while droplets 10 micrometers in diameter travel 200 times farther. Droplets less than 50 micrometers in size can frequently remain airborne long enough to reach ceiling ventilation units.” The video at this link shows droplets moving 6-8 meters (20-26 feet), considerably farther than the 6 foot droplet precaution put forth by CDC.

Extensive Viable Middle East Respiratory Syndrome (MERS) Coronavirus Contamination in Air and Surrounding Environment in MERS Outbreak Units explored the possible contribution of contaminated hospital air and surfaces to MERS transmission by collecting air and swabbing environmental surfaces in 2 hospitals treating MERS-CoV patients. The study shows clearly droplet precaution isn’t working. The presence of MERS-CoV was confirmed by reverse transcription polymerase chain reaction (RT-PCR) of viral cultures of 4 of 7 air samples from 2 patients’ rooms, 1 patient’s restroom, and 1 common corridor. In addition, MERS-CoV was detected in 15 of 68 surface swabs by viral cultures. Immunofluorescence assay (IFA) on the cultures of the air and swab samples revealed the presence of MERS-CoV. EM images also revealed intact particles of MERS-CoV in viral cultures of the air and swab samples. The study concludes: These data provide experimental evidence for extensive viable MERS-CoV contamination of the air and surrounding materials in MERS outbreak units. Thus, our findings call for epidemiologic investigation of the possible scenarios for contact and airborne transmission, and raise concern regarding the adequacy of current infection control procedures.


Dirty floors are an often overlooked component of infection control

dirty floorAddressing dirty floors is a key, often overlooked, component of infection control. Walking on dirty floors aerosolizes the bacteria and virus back into the air potentially contaminating another surface or it is inhaled. Resuspension of particles – be it bacteria, chemical, viral or particulate matter – impacts health. The copious data that exists suggests strongly that it is a threat that must be recognized.

RESUSPENSION OF ALLERGEN-CONTAINING PARTICLES UNDER MECHANICAL AND AERODYNAMIC FORCES FROM HUMAN WALKING – INTRODUCTION TO AN EXPERIMENTAL CONTROLLED METHODOLOGY. In this study, a reliable and reproducible methodology was developed to explore the influence of human walking on the aerosolization of allergen-containing particles. It finds that: Peak resuspension factor (RF) and resuspension rate (RR) measured in these experiments ranged from 10-6 to 10-3 m-1 and 10-5 to 10-2 min-1, while average RF and RR ranged from 10-8 to 10-4 m-1 and 10-7 to 10-3 min-1, respectively. Despite the four order of magnitude range, these values fall between field measured values found in the literature review. The main observations derived from the experiments performed were: (1) for a continuous disturbance, resuspension was only observed during the first two minutes with an initial burst of particle reentrainment followed by an exponential decrease to undetectable value; (2) air-puff disturbances had a much higher impact on dust resuspension than the vibration disturbances; (3) particles were more easily resuspended from linoleum flooring than from carpet flooring; (4) German roach dust was more easily resuspended by air streams than quartz dust; (5) RF and RR values derived from the present experiments show consistency with previous research values

The methodology presented has been demonstrated and proven to be a valuable tool to gather reliable information on particle resuspension. The controlled environmental and disturbance conditions, the flexibility to generate different types of disturbances (including a future electrostatic disturbance), the broad range and flexibility of air sampling, the flexibility to use different flooring and different dust such as allergen containing dust and surrogate CBW dusts make it a potential useful tool for particle resuspension research and thereby contribute to the development of exposure risk models.

An evaluation of the impact of flooring types on exposures to fine and coarse particles within the residential micro-environment using CONTAM is found at the Journal of Exposure Science & Environmental Epidemiology. It shows that both flooring type and floor loading had significant impact on incremental concentrations of both fine and coarse particulate matter (PM) due to resuspension from walking.

Surrounded by a Cloud of Dust: Particle Resuspension in Indoor Environments is a splendid presentation by Brandon E. Boor, Ph.D. Assistant Professor of Civil Engineering, Purdue University, at a meeting of the National Academies of Science, Engineering and Medicine.

Indoor and outdoor air pollution can cause great harm to health

burnerAir pollution, particulate and specific chemicals, can exacerbate COPD and the onset of asthma as well as increase the respiratory morbidity and mortality. Globally, seven million deaths were attributable to the joint effects of household and ambient air pollution. Subjects with chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma are especially vulnerable to the detrimental effects of air pollutants. For reducing the air pollutants indoor, people should use clean fuels and improve the stoves so as to burn fuel more efficiently and vent emissions to the outside. Air cleaners that can improve the air quality efficiently are recommended. Air pollution and chronic airway diseases: what should people know and do? provides a nice rundown of pollution sources and their potential negative impact.

The World Health Organization estimates that 7 million premature deaths annually linked to air pollution. That’s one in eight deaths globally, making it the single largest environmental health risk. Reducing pollution could save millions of lives.

Outdoor Air and Appliances as Sources of Indoor Particulate Matter is an enlightening YouTube piece that features Brent Stephens, Ph.D. Assistant Professor of Architectural Engineering, Illinois Institute. He discusses factors affecting indoor air quality as part of an Environmental Protection Agency meeting.


Sneeze droplets shown to travel farther than conventionally believed

sneezeThe snot-spattered experiments that show how far sneezes really spread. Mathematician Lydia Bourouiba uses high-speed video to break down the anatomy of sneezes and coughs — and to understand infectious disease. In this piece at Nature, Corie Lok writes: Bourouiba’s goal is to “ground epidemiology and public health in physics and mathematics. When trying to keep diseases from running rampant, she says, “we want to be giving recommendations that are based on science that has been tested in the lab”. In practical terms, such insights could lead to maps showing the contamination risks in the vicinity of infected people, protective equipment optimized to shield hospital workers from specific kinds of germs, and better predictions of how diseases move through a population.

Lok goes on to write: The video evidence (shown wonderfully at this link) contradicted conventional thinking about sneezes, which held that larger droplets would fall to the ground within 1–2 metres, and that only the smaller ones would stay aloft as airborne aerosols. Feeding her video evidence into her mathematical models, Bourouiba concluded that, thanks to the cloud dynamics, many of the larger droplets can travel up to 8 metres for a sneeze and 6 metres for a cough, depending on the environmental conditions, and stay suspended for up to 10 minutes — far enough and long enough to reach someone at the other end of a large room, not to mention the ceiling ventilation system. That conclusion has implications for health-care workers, says James Hughes, an infectious-disease epidemiologist at Emory University in Atlanta. If a disease is thought to be transmitted within 1–2 metres, workers might assume that they are safe beyond that zone. “I think maybe we need to be a little bit more circumspect about that,” he says.

Aerosolized bacteria come from many sources. When you look at particle size you can really see how disease spreads through the air and on to other surfaces. Combine all this with bacterial and viral shedding, and it is easy to see how standard cleaning practices cannot keep up with the contamination levels.

In the cloud: How coughs and sneezes float farther than you think debunks Centers for Disease Control data droplet precaution that is set at 6 feet. As science advances, we have to rethink continually.

A High-Speed Super Zoomed Video Of What Happens To A Toilet When You Flush: You think you’re cleaning up the mess, but it’s just making it worse. That’s very bad in places where they’re trying to have no messes at all—like, say, a hospital. Aerosolized bacteria come from many sources.  When you look at particle size you can really see how disease spreads through the air and on to other surfaces. Combine all this with bacterial and viral shedding it is easy to see how standard cleaning practices cannot keep up with the contamination levels.


Deadly MRSA enjoys variety of transmission paths

MRSAMRSA is methicillin-resistant Staphylococcus aureus, a type of staph bacteria that is resistant to several antibiotics. In the general community, MRSA most often causes skin infections. In some cases, it causes pneumonia (lung infection) and other issues. If left untreated, MRSA infections can become severe and cause sepsis – a life-threatening reaction to severe infection in the body.  MRSA can be transmitted in a variety of ways. Below, we look at some studies and articles that look more closely at MRSA and explore methods of transmission.

Significance of Airborne Transmission of Methicillin-Resistant Staphylococcus aureus in an Otolaryngology–Head and Neck Surgery Unit sets out to quantitatively investigate the existence of airborne methicillin-resistant Staphylococcus aureus (MRSA) in a hospital environment and to perform phenotyping and genotyping of MRSA isolates to study MRSA epidemiology. It concludes: MRSA was re-circulated among the patients, the air, and the inanimate environments, especially when there was movement in the rooms. Airborne MRSA may play a role in MRSA colonization in the nasal cavity or in respiratory tract MRSA infections. Measures should be taken to prevent the spread of airborne MRSA to control nosocomial MRSA infection in hospitals.

MRSA model of learning and adaptation: a qualitative study among the general public, at BioMed Central, looks at a study that allowed participants to tell their stories in a effort to understand MRSA better. It concludes that the study “underscores the critical importance of educational programs for patients, and improved continuing education for healthcare providers. Five specific results of this study can reduce the vacuum that currently exists between the knowledge and information available to healthcare professionals, and how that information is conveyed to the public. These points include: 1) a common model of MRSA learning and adaptation; 2) the self-directed nature of adult learning; 3) the focus on general MRSA information, care and prevention, and antibiotic resistance; 4) the interconnected nature of adaptation; and, 5) the need for a consistent step by step plan to deal with MRSA provided at the time of diagnosis.”

Superbug colony behaviors revealed in time lapse video indicates that MRSA, thought to have been a static or non-motile organism, has been observed showing signs of active motility by scientists at The Universities of Nottingham and Sheffield. The video is pretty incredible.

Drug-resistant MRSA bacteria: Here to stay in both hospital, community says that MRSA, once confined to hospitals but now widespread in communities, will likely continue to exist in both settings as separate strains, according to a new study. The prediction that both strains will coexist is reassuring because previous projections indicated that the more invasive and fast-growing community strains would overtake and eliminate hospital strains, possibly posing a threat to public health.

Related good reads: