PE Overshoes
PE Overshoes, Disposable PE Overshoes, PE Overshoes supp
PE Overshoes, Disposable PE Overshoes, PE Overshoes supp
Disposable KN95 Face Mask Material: Needle punched cotto
Disposable Medical Mask Material: NonWoven Fabric+Meltbl
Disposable N95 Mask Material: 5 ply Non-woven fabric Col
Infrared Forehead Thermometer Sample: Free Brand: Orient
General purpose, Cleanroom, Construction/building, Clean
Disposable Medical Gloves Material: PVC Color: Transpare
The Respiratory Route of Transmission
A respiratory pathogen may be transmitted via three routes—contact, droplet, and airborne spread. Contact transmission may be direct (i.e., transfer of virus via contaminated hands) or indirect (i.e., via fomites) . Fomites are objects or materials that may carry infection, and spread by fomites means spread by touch. Viruses do survive for some time on inanimate objects, although the viral load declines dramatically. If we touch a contaminated surface and then touch our eyes or nose, we may inoculate the virus into our mucosal surfaces. The role of touch in the spread of a respiratory virus is best exemplified by studies of the Respiratory Syncytial Virus (RSV) . The spread of SARS-CoV-2 via fomites has been elegantly demonstrated by real-world contact tracing, aided by closed-circuit cameras.
Droplet spread and airborne spread are different modes of transmission of the virus through the air. Viruses released when an infected person coughs, sneezes, sings, talks, or merely exhales may be found in particles of varying sizes. Generally, particles larger than 5 μm were thought to fall to the ground within 1 metre. More recently, however, the “gas cloud” hypothesis has been proposed. Coughing, sneezing, or even exhaling produces mucosalivary droplets that exist as part of a cloud that “carries within it clusters of droplets with a continuum of droplet sizes”. In combination with environmental factors, the “cloud” may be propelled up to 7–8 m. Wind speed, in particular, has been shown to play a role in determining the distance travelled by these particles.
Airborne spread occurs with pathogens found in exhaled μm in diameter. These particles remain afloat for some time and are able to travel long distances. Respiratory viruses accepted as being capable of spread via the airborne route include measles and varicella zoster (chickenpox). These viruses have a large , a feature thought to characterise spread by the airborne route. Interestingly, influenza, coronavirus, and rhinovirus RNA, generally thought to be transmitted by the droplet route, can be found in exhaled particles smaller or larger than 5 μm. Further, viable influenza is present in particles smaller than 5 μm. Hence, even viruses thought to be transmitted primarily by the respiratory droplet route may have the potential for airborne spread. Concern that SARS-CoV-2 may spread by the airborne route rose when it was shown to be viable for 3 hours in a drum that artificially kept particles afloat for several hours.
It might be less well known that more basic processes like talking can also lead to the release of potentially infectious droplets and aerosols. Using laser light scattering, it was found that there were average emissions of about 1000 droplet particles per second during speech, with high emission rates of up to 10,000 droplet particles per second. By fitting the time-dependent decrease in particle detected to exponential decay times, the droplet particle sizes and estimated viral load could be calculated.
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