Current Updates on Transmission of Virus
Fluid dynamics of respiratory droplets in the context of COVID-19: Airborne and surfaceborne transmissions
Cite as: Phys. Fluids 33, 081302 (2021); https://doi.org/10.1063/5.0063475
The World Health Organization has declared COVID-19 a global pandemic. Several countries have experienced repeated periods of major
spreading over the last two years. Many people have lost their lives, employment, and the socioeconomic situation has been severely
impacted. Thus, it is considered to be one of the major health and economic disasters in modern history. Over the last two years, several
researchers have contributed significantly to the study of droplet formation, transmission, and lifetime in the context of understanding the
spread of such respiratory infections from a fluid dynamics perspective. The current review emphasizes the numerous ways in which fluid
dynamics aids in the comprehension of these aspects. The biology of the virus, as well as other statistical studies to forecast the pandemic, is
significant, but they are not included in this review.
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Effect of Ultraviolet Germicidal Irradiation on Viral Aerosols
Environ. Sci. Technol. 2007, 41, 5460-5465
University of Texas Health Science Center at Houston, Houston, TX, and Department of Environmental Health, Institute of Health and Environment, Seoul National University, Seoul, Korea
Ultraviolet (UV) germicidal air disinfection is an
engineering method used to control the airborne
transmission of pathogenic microorganisms in
high-risk settings. Despite the recent emergence of
respiratory viral pathogens such as SARS and avian
influenza viruses, UV disinfection of pathogenic
viral aerosols has not been examined. Hence, we
characterized the UV disinfection of viral aerosols using
the bacteriophage MS2, adenovirus, and coronavirus.
Our objectives were to characterize the effect of
nebulization and air sampling on the survival of
important viral pathogens, quantitatively characterize
and estimate the UV susceptibility of pathogenic
viral aerosols, and evaluate the effect of relative
humidity (RH) on the susceptibility of viral aerosols,
to 254 nm UV-C. The viruses were aerosolized into
an experimental chamber using a six-jet Collison
nebulizer, exposed to 254 nm UV, and sampled
using an AGl-30 liquid impinger. Both the MS2 and
adenovirus aerosols were very resistant to UV air
disinfection, with a reduction of less than 1 logarithm
in viable viral aerosols at a UV dose of 2608 чtW s/
cm2• The susceptibility of coronavirus aerosols was
7-10 times that of the MS2 and adenovirus aerosols.
Unlike bacterial aerosols, there was no significant
protective effect of high RH on UV susceptibility of
the tested viral aerosols. We confirmed that the UV
disinfection rate differs greatly between viral aerosols
and viruses suspended in liquid
Far-UVC light efficiently and safely inactivates airborne human coronaviruses
SCIENTIFIC REPORTS I (2020) 10:10285 I https://doi. org/10.1038/s41598-020-67211-2
A direct approach to limit airborne viral transmissions
is to inactivate them within a short time of their
production. Germicidal ultraviolet light, typically at
254 nm, is effective in this context but, used directly,
can be a health hazard to skin and eyes. By contrast,
far-UVC light (207-222 nm) efficiently kills pathogens
potentially without harm to exposed human tissues. We
previously demonstrated that 222-nm far-UVC light
efficiently kills airborne influenza virus and we extend
those studies to explore far-UVC efficacy against
airborne human coronaviruses alpha HCoV-229E and
beta HCoV-OC43. Low doses ofl.7 and 1.2 mJ/cm2
inactivated 99.9% of aerosolized coronavirus 229E
and OC43, respectively. As all human coronaviruses
have similar genomic sizes, far-UVC light would be
expected to show similar inactivation efficiency against
other human coronaviruses including SARS-CoV-2.
Based onthe beta-HCoV-OC43 results, continuous
far-UVC exposure in occupied public locations at
the current regulatory exposure limit (-3 mJ/cm2/
hour) would result in -90% viral inactivation in -8
minutes, 95% in -11 minutes, 99% in -16 minutes and
99.9% inactivation in -25 minutes. Thus while staying
within current regulatory dose limits, low-doserate far-UVC exposure can potentially safely provide
a major reduction in the ambient level of airborne
coronaviruses in occupied public locations.
What Scientists Know About Airborne Transmission of the New Coronavirus
Smithsonian Aug 12, 2020
Aerosol experts, from engineers to doctors, weigh in on the ability of tiny droplets to transmit the virus that causes COVID-19.
Over the past few months, an increasing number of scientists, clinicians, and engineers have called for greater recognition that aerosols, in addition to larger droplets can transmit the novel coronavirus that causes COVID-19. While the difference is literally miniscule, acknowledging this route of transmission would result in significant changes in how the public can bring an end to the global pandemic. In the near term, it would inform social distancing and mask wearing recommendations from local governments, and in the long term, engineers and architects will need to rethink ventilation and air filtration in the design of everything from schools to cruise ships.
Aerosols are microscopic particles that can remain
airborne for… more
Protecting against COVID’s Aerosol Threat
Scientific American Oct 1.2020
How can we make our schools, office buildings and homes safer?
This feels like a lopsided fight. In one corner, we have scientists, epidemiologists, infectious-disease physicians, clinicians, engineers—many different experts in the medical community, that is—arguing that the spread of COVID-19 by aerosols (that is, tiny droplets that can remain airborne long enough to travel significantly farther than the six-foot separation we’ve been told to observe) is both real and dangerous. In the other, it’s the Centers for Disease Control (CDC) and the World Health Organization (WHO), which until very recently have allowed only that aerosol spread is possible, not necessarily likely.
And while watching experts going against governmental agencies isn’t always riveting stuff, this particular battle is terribly .. more
The Application of Ultraviolet Germicidal Irradiation to Control Transmission of Airborne Disease: Bioterrorism Countermeasure
PUBLIC HEALTH REPORTS / MARCH-APRIL 2003 / VOLUME 118
SYNOPSIS
Bioterrorism is an area of increasing public health
concern. The intent of this article is to review the air
cleansing technologies available to protect building
occupants from the intentional release of bioterror
agents into congregate spaces (such as offices,
schools, auditoriums, and transportation centers),
as well as through outside air intakes and by way of
recirculation air ducts. Current available technologies
include increased ventilation, filtration, and ultraviolet
germicidal irradiation (UVGI) UVGI is a common tool
in laboratories and health care facilities, but is not
familiar to the public, or to some heating, ventilation,
and air conditioning engineers. Interest in UVGI is
increasing as concern about a possible malicious
release of bioterror agents mounts. Recent applications
of UVGI have focused on control of tuberculosis
transmission, but a wide range of airborne respiratory pathogens are susceptible to deactivation by UVGI.
In this article, the authors provide an overview of air
disinfection technologies, and an in-depth analysis
of UVGl-its history, applications, and effectiveness.
Airborne transmission of SARS-CoV-2
Science Magazine Oct 16, 2020
There is overwhelming evidence that inhalation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represents a major transmission route for coronavirus disease 2019 (COVID-19). There is an urgent need to harmonize discussions about modes of virus transmission across disciplines to ensure the most effective control strategies and provide clear and consistent guidance to the public. To do so, we must clarify the terminology to distinguish between aerosols and droplets using a size threshold of 100 µm, not the historical 5 µm (1). This size more effectively separates their aerodynamic behavior, ability to be inhaled, and efficacy of interventions.
Viruses in droplets (larger than 100 µm) typically fall to the ground in seconds within 2 m of the source and can be sprayed like tiny cannonballs onto … more
239 Experts With One Big Claim: The Coronavirus Is Airborne
New York Times 2020/07/04
The W.H.O. has resisted mounting evidence that viral particles floating indoors are infectious, some scientists say. The agency maintains the research is still inconclusive.
Patrons at the Ocean Casino in Atlantic City, N.J., on July 3. Some scientists are warning that airborne transmission of the coronavirus in indoor settings has
been underappreciated. Patrons at the Ocean Casino in Atlantic City, N.J., on July 3. Some scientists are warning that airborne transmission of the coronavirus in indoor settings has been underappreciated.
The coronavirus is finding new victims worldwide, in bars and restaurants, offices, markets and casinos, giving rise to frightening clusters of infection that increasingly confirm what many scientists have been saying for months: The virus lingers in the air indoors, infecting those nearby… more
CDC Acknowledges Covid-19 Can Spread Via Tiny Air Particles
Wall Street Journal Oct. 5, 2020
The agency updates guidelines after previously deleting language on airborne particles; virus can spread to people more than 6 feet away.
The U.S. Centers for Disease Control and Prevention said tiny particles that linger in the air can spread the coronavirus, revising its guidelines on the matter just a few weeks after the health agency had acknowledged a role for the particles and then abruptly removed it.
The guidelines on how the coronavirus spreads were initially updated last month to acknowledge a role, and possibly the primary one, played by tiny aerosol particles in spreading the virus. But the agency removed the changes only days later, saying a draft… m more