The potential for aerosol transmission of infectious influenza virus (ie, in healthcare facilities) is controversial. We constructed a simulated patient examination room that contained coughing and breathing manikins to determine whether coughed influenza was infectious and assessed the effectiveness of an N95 respirator and surgical mask in blocking transmission.
National Institute for Occupational Safety and Health aerosol samplers collected size-fractionated aerosols for 60 minutes at the mouth of the breathing manikin, beside the mouth, and at 3 other locations in the room. Total recovered virus was quantitated by quantitative polymerase chain reaction and infectivity was determined by the viral plaque assay and an enhanced infectivity assay.
Infectious influenza was recovered in all aerosol fractions (5.0% in >4 μm aerodynamic diameter, 75.5% in 1-4 μm, and 19.5% in <1 μm; n = 5). Tightly sealing a mask to the face blocked entry of 94.5% of total virus and 94.8% of infectious virus (n = 3). A tightly sealed respirator blocked 99.8% of total virus and 99.6% of infectious virus (n = 3). A poorly fitted respirator blocked 64.5% of total virus and 66.5% of infectious virus (n = 3). A mask documented to be loosely fitting by a PortaCount fit tester, to simulate how masks are worn by healthcare workers, blocked entry of 68.5% of total virus and 56.6% of infectious virus (n = 2).
These results support a role for aerosol transmission and represent the first reported laboratory study of the efficacy of masks and respirators in blocking inhalation of influenza in aerosols. The results indicate that a poorly fitted respirator performs no better than a loosely fitting mask.
"There has been a lot of emphasis on detection of VOCs using gas analysis or condensates   , however few studies have been aimed at the capture detection of microorganisms in exhaled breath. Specifically, aerosols with droplet size >1 m are formed through coughing      and are targeted in our work. "
[Show abstract][Hide abstract] ABSTRACT: In this work, the development of a point-of-care (PoC) system to capture aerosol from litres of air directly onto a microfluidic lab-on-chip for subsequent analysis is addressed. The system involves an electrostatic precipitator that uses corona charging and electrophoretic transport to capture aerosol droplets onto a microfluidic air-to-liquid interface for downstream analysis. A theoretical study of the governing geometric and operational parameters for optimal electrostatic precipitation is presented. The fabrication of an electrostatic precipitator prototype and its experimental validation using a laboratory-generated aerosolized dye is described. Collection efficiencies were comparable to those of a state-of-the-art Biosampler impinger, with the significant advantage of providing samples that are at least 10 times more concentrated. Finally, we discuss the potential of such a system for breath-based diagnostics.
Sensors and Actuators B Chemical 02/2015; 212. DOI:10.1016/j.snb.2015.02.008 · 4.10 Impact Factor
"Simply testing aerosols by RT-PCR for detection of viral nucleic acid would not be sufficient to demonstrate that the viruses in fine particles remain infectious. Given the extensive debate in the literature   and the likelihood that a large percentage of viral copies detected by molecular methods are defective  , it would be important for new studies to quantify infectious viruses and not merely measure the total viral RNA copy numbers. Based on RT-PCR assay and the influenza virus stock used for calibration, Fabian, with colleagues , established a ratio of 300 copies per TCID 50 , which is well within the previously published estimates of 100–350 or 650   "
[Show abstract][Hide abstract] ABSTRACT: Influenza is one of the most contagious and rapidly spreading infectious diseases and an important global cause of hospital admissions and mortality. There are some amounts of the virus in the air constantly. These amounts is generally not enough to cause disease in people, due to infection prevention by healthy immune systems. However, at a higher concentration of the airborne virus, the risk of human infection increases dramatically. Early detection of the threshold virus concentration is essential for prevention of the spread of influenza infection. This review discusses different approaches for measuring the amount of influenza A virus particles in the air and assessing their infectiousness. Here we also discuss the data describing the relationship between the influenza virus subtypes and virus air transmission, and distribution of viral particles in aerosol drops of different sizes.
Advances in Virology 08/2014; 2014:859090. DOI:10.1155/2014/859090
"Simply testing aerosols by reverse transcription, quantitativepolymerase chain reaction (RT-qPCR) for detection of viral nucleic acid would not be sufficient to demonstrate that the viruses in fine particles remain infectious. Given the extensive debate in the literature (Tellier 2006; Brankston et al. 2007) and the likelihood that a large percentage of viral copies detected by molecular methods are defective (Fabian et al. 2009a; Noti et al. 2012), it would be important for new studies to quantify infectious virus and not merely measure the total viral RNA copy numbers. Our goal was to design and evaluate the performance of an exhaled-breath sampling device that can characterize infectious influenza aerosols emitted from infected persons who are wearing masks and performing various respiratory maneuvers (i.e., tidal breathing, talking, and coughing). "
[Show abstract][Hide abstract] ABSTRACT: The importance of the aerosol mode for transmission of influenza is unknown. Understanding the role of aerosols is essential to developing public health interventions such as the use of surgical masks as a source control to prevent the release of infectious aerosols. Little information is available on the number and size of particles generated by infected persons, which is partly due to the limitations of conventional air samplers, which do not efficiently capture fine particles or maintain microorganism viability. We designed and built a new sampler, called the G-II, that collects exhaled breath particles that can be used in infectivity analyses. The G-II allows test subjects to perform various respiratory maneuvers (i.e. tidal breathing, coughing, and talking) and allows subjects to wear a mask or respirator during testing. A conventional slit impactor collects particles > 5.0 μm. Condensation of water vapor is used to grow remaining particles, including fine particles, to a size large enough to be efficiently collected by a 1.0 μm slit impactor and be deposited into a buffer-containing collector. We evaluated the G-II for fine particle collection efficiency with inert particle aerosols and evaluated infective virus collection using influenza A virus aerosols. Testing results showed greater than 85% collection efficiency for particles greater than 50nm and influenza virus collection comparable with a reference SKC BioSampler®. The new design will enable determination of exhaled infectious virus generation rate and evaluate control strategies such as wearing a surgical type mask to prevent the release of viruses from infected persons.
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