PDF Publication Title:
Text from PDF Page: 002
C.P. Sabino, et al. Journal of Photochemistry & Photobiology, B: Biology 212 (2020) 111999 However, since most UV-C light is filtered by the atmospheric ozone layer, in practical terms, the antimicrobial activity associated with sunlight is mostly caused by photochemical reactions induced by UV-A and UV-B photons which are absorbed by endogenous chromophores such as amino acid residues, flavins, and porphyrin derivatives [25]. While UV-A alone does not seem to exert any significant virucidal ef- fects, natural and artificial sunlight, as well as radiation in the UV-B spectrum, have been shown to inactivate bacteriophages and human viruses [26]. A model for the potential of solar UV radiation to in- activate viruses aerosolized in the atmosphere concluded that a full day of sun exposure would on average decrease the infectivity of UV-sen- sitive viruses by 3 log10 [27]. Besides its virucidal potential, solar UV radiation can also play a protective role against infectious diseases via its modulating effect on vitamin D production [28]. Vitamin D is known to upregulate the production of human cathelicidin, LL-37. This antimicrobial peptide has both antimicrobial and antiendotoxin activities, and also attenuates the production of proinflammatory cytokines which typically accompany respiratory tract infections. Accordingly, it was recently suggested that vitamin D could reduce the incidence, severity, and risk of death due to respiratory tract infections, notably those caused by COVID-19 [29]. However, conclusive evidence for an association between vitamin D supplementation and decreased risk of respiratory tract infections is still lacking. UV-C is directly absorbed by pyrimidine bases causing their di- merization, which leads to viral inactivation via DNA or RNA damage [30]. Thymine is the main chromophore in DNA while uracil is its counterpart in RNA. Upon UV-C exposure, thymine and uracil form cyclobutane-dimers and pyrimidine-protein cross-links [30]. It must be stressed that UV-C usage must be limited to inanimate objects since it is highly dangerous to human skin. The viral protein coat has been shown to protect nucleic acids from UV-C radiation, by shielding the RNA, quenching the excited states of RNA, and/or by surrounding the bases with a hydrophobic environment and limiting the mobility of the in- dividual bases. This results in a reduction of the overall rate of photo- reactions, which allows the formation of non-cyclobutane-type dipyr- imidines and uridine hydrates. Viral coating proteins themselves may suffer UV photodamage and become cross-linked to RNA. The International Ultraviolet Association (IUVA) recently released a fact sheet detailing the efficacy of UV on SARS-CoV-2 [31] in which they reviewed all the appropriate requirements for the safety of UV-C disinfection devices and discussed the corresponding performance standards and validation protocols. Coronaviruses display a wide range of UV-C LD90 (UV-C dose necessary to2inactivate 90% of a microbial population) values, from 7 to 241 J/m so one might assume that the UV-C susceptibility of the novel SARS-CoV-2 (COVID-19) virus prob- ably lies within this range [32]. Therefore, based on previous studies with SARS-CoV-1 and other RNA-based coronaviruses, UV-C light can be used to effectively inactivate such pathogens present in the air, li- quids and over several surfaces [33,34]. 5. Ultraviolet Germicidal Irradiation (UVGI) UV-C lamps have long been used in hospital and industrial settings for decontamination purposes. In the context of a mitigation approach to infection spreading, UV-C can be particularly helpful in the in- activation of virus-containing aerosols and surfaces. Air disinfection via upper-room germicidal UV-C light fixtures may be able to reduce viral transmission via the airborne route. Accordingly, an observational study during the 1957 influenza pandemic reported that patients housed in hospital wards with upper-room UV-C had an infection rate of 1.9%, compared to an infection rate of 18.9% among patients housed in wards without UV-C [35]. However, it is important to note that the germicidal effect of UV-C seems to be strongly depen- dent on the relative humidity of the air, with UV-C effectiveness against influenza virus decreasing with increasing relative humidity [36]. personal protective equipment (PPE), including eyewear, N95 re- spirators, and masks. Additionally, photobiomodulation, a light-based anti-inflammatory therapy, may have some palliative effects on patients suffering from severe COVID-19. This review examines the potential of light-based technologies to prevent COVID-19 infection and control its dissemination by direct viral inactivation and to treat COVID-19 by modulating the host immune system. The direct antimicrobial actions of solar and UV radiation, photodynamic therapy, antimicrobial blue light, and ultrafast pulsed lasers for disinfection or in vivo use are considered, and the application of photobiomodulation to stimulate the host to mount an anti-viral response is discussed. 2. SARS-CoV-2 Stability Outside The Human Body SARS-CoV-2 is highly infectious [15] and transmission occurs through contaminated air, water, and surfaces, which plays a pivotal role in its unbridled dissemination. A recent study by van Doremalen and colleagues investigated the stability of SARS-CoV-2 in aerosols and on inanimate surfaces (e.g., glass, metal, plastic, or cardboard) that can act as important transmission vectors [16]. Their findings suggest that aerosol and fomite transmission of SARS-CoV-2 is likely, indicating that the virus can remain viable and infectious for hours in aerosols and up to days on surfaces. This is in agreement with a recent comparative analysis of 22 studies looking at the persistence of a broader panel of human coronaviruses on inanimate surfaces [17] This study included prominent pathogenic coronavirus species such as Severe Acute Re- spiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) and endemic human coronaviruses (HCoV) and concluded that: 1) viruses can remain infectious from 2 h to 9 days; 2) incubation tem- perature is critical, as some viruses can remain viable at 4 °C for up to 28 days whereas at 30–40 °C viral viability is reduced. 3. Historical Milestones of Antimicrobial Light The microbicidal effects of light have been widely known for more than a century. In 1885, Duclaux experimented with several microbial species and concluded that “sunlight is the best, cheapest, and most universally applicable microbicidal agent that we have” [18]. As early as 1877, Downes and Blunt observed that light could effectively kill a series of microorganisms and reported that this effect was dependent on light parameters such as intensity, duration (i.e., light dose) and that the shortest wavelengths (e.g., blue to ultraviolet light) were the most ef- fective [19] The first report on the virucidal effects of UV radiation dates back to 1928 when Rivers and Gates used UV light to inactivate viral particles in suspension and proved the efficacy of the method through subsequent subcutaneous inoculation of rabbits [20]. In 1903, Niels Finsen was awarded the Nobel Prize in Physiology or Medicine for his contribution to the treatment of infectious diseases, especially cutaneous tuberculosis, using visible light [21,22]. Virtually at the same time, Herman Von Tappeiner and Oscar Raab discovered by accident that the use of fluorescent dyes could enhance the microbial killing effect of visible light via photodynamic reactions [22]. By the 1930s, germicidal low-pressure Mercury (Hg) discharge lamps emitting quasi-monochromatic UV-C light (peak emission at 254 nm) had been introduced into the market as highly efficient disinfection equipment [23]. Thus, since the pre-antibiotic era, light-based strategies have been extensively studied and used to treat and prevent infections [24]. However, each photoinactivation strategy has its pros and cons that must be carefully considered when designing a new microbial control strategy. 4. Natural Ultraviolet Light Ultraviolet (UV) radiation is naturally and ubiquitously emitted by the sun, representing 10% of its total light output. Only a small portion of the sunlight spectra has direct antimicrobial properties (UV-C). 2PDF Image | A Light-based technologies for management of COVID-19 pandemic
PDF Search Title:
A Light-based technologies for management of COVID-19 pandemicOriginal File Name Searched:
light-based-covid-pandemic-management.pdfDIY PDF Search: Google It | Yahoo | Bing
Cruise Ship Reviews | Luxury Resort | Jet | Yacht | and Travel Tech More Info
Cruising Review Topics and Articles More Info
Software based on Filemaker for the travel industry More Info
The Burgenstock Resort: Reviews on CruisingReview website... More Info
Resort Reviews: World Class resorts... More Info
The Riffelalp Resort: Reviews on CruisingReview website... More Info
| CONTACT TEL: 608-238-6001 Email: greg@cruisingreview.com | RSS | AMP |