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The potential virucidal effects of UV-C irradiation on SARS-CoV-2 were experimentally evaluated for different illumination doses and virus concentrations (1000, 5, 0.05 MOI). At a virus density comparable to that observed in SARS-CoV-2 infection, an UV-C dose of just 3.7 mJ/cm2 was sufficient to achieve a more than 3-log inactivation without any sign of viral replication. Moreover, a complete inactivation at all viral concentrations was observed with 16.9 mJ/cm2. These results could explain the epidemiological trends of COVID-19 and are important for the development of novel sterilizing methods to contain SARS-CoV-2 infection.
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Scientic Reports | (2021) 11:6260 | 
UV‑C irradiation is highly eective
in inactivating SARS‑CoV‑2
Mara Biasin1, Andrea Bianco2, Giovanni Pareschi2, Adalberto Cavalleri3, Claudia Cavatorta3,
Claudio Fenizia1,6, Paola Galli2, Luigi Lessio4, Manuela Lualdi5, Enrico Tombetti1,
Alessandro Ambrosi6, Edoardo Maria Alberto Redaelli2, Irma Saulle1,7, Daria Trabattoni1,
Alessio Zanutta2 & Mario Clerici7,8*
The potential virucidal eects of UV‑C irradiation on SARS‑CoV‑2 were experimentally evaluated
for dierent illumination doses and virus concentrations (1000, 5, 0.05 MOI). At a virus density
comparable to that observed in SARS‑CoV‑2 infection, an UV‑C dose of just 3.7 mJ/cm2 was sucient
to achieve a more than 3‑log inactivation without any sign of viral replication. Moreover, a complete
inactivation at all viral concentrations was observed with 16.9 mJ/cm2. These results could explain
the epidemiological trends of COVID‑19 and are important for the development of novel sterilizing
methods to contain SARS‑CoV‑2 infection.
e COVID-19 pandemic caused by SARS-CoV-2 virus1 has had an enormous, as yet barely understood, impact
on health and economic outlook at the global level2. e identication of eective microbicide approaches is
of paramount importance in order to limit further viral spread, as the virus can be transmitted via aerosol3,4
and can survive for hours outside the body57. Non-contact disinfection technologies are highly desirable, and
UV radiation, in particular UV-C (200–280nm) has been suggested to be able to inactivate dierent viruses,
including SARS-CoV812. e interaction of UV-C radiations with viruses has been extensively studied1315, and
direct absorption of the UV-C photon by the nucleic acid basis and/or capsid proteins leading to the genera-
tion of photoproducts that inactivate the virus was suggested to be one of the main UV-C-associated virucidal
mechanisms16,17. Some models have been proposed to correlate the nucleic acid structure with the required dose
to inactivate the virus, but a reliable model is still unavailable18. is is also due to the fact that UV-C measure-
ments were conducted using dierent viruses and diverse experimental conditions1922. is led to an extremely
wide range of values for the same virus and, e.g., in the case of SARS-CoV-1 values reported in the literature
range from a few mJ/cm2 to hundreds mJ/cm219,22,23. Likewise, recent papers reported values for UVC inactivation
ranging from 3 to 1000mJ/cm22427. A better understanding of the eects of UV-C on SARS-CoV-2, which take
into account all the key factors involved in the experimental setting (including culture medium, SARS-CoV-2
concentration, UV-C irradiance, time of exposure, and UV-C absorbance) will allow to replicate the results in
other laboratory with dierent devices. Moreover, as recent evidences suggest that UV light from sunlight are
ecient in inactivating the virus28, these measurements will be relevant for the setting up of further experiment
considering the role of UV-A and UV-B on SARS-CoV-2 replication.
Results and discussion
Herein, we report the eect of monochromatic UV-C (254nm) on SARS-CoV-2, showing that virus inactivation
can be easily achieved. Experiments were conducted using a custom-designed low-pressure mercury lamp system,
which has been spectral-calibrated providing an average intensity of 1.082 mW/cm2 over the illumination area
(see the details reported in the Method section). ree dierent illumination exposure times, corresponding to
3.7, 16.9 and 84.4mJ/cm2, were administered to SARS-CoV-2 either at a multiplicity of infection (MOI) of 0.05, 5,
1000. e rst concentration is equivalent to the low-level contamination observed in closed environments (e.g.
Department of Biomedical and Clinical Sciences L. Sacco, University of Milan, Milan, Italy. Italian National
       Epidemiology and Prevention
Unit, IRCCS Foundation, Istituto Nazionale dei Tumori, Milan, Italy. Italian National Institute for Astrophysics
     Department of Imaging Diagnostic and Radioterapy,
IRCCS Foundation, Istituto Nazionale dei Tumori, Milan, Italy.       
Italy. Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy. Don C. Gnocchi
Foundation, IRCCS Foundation, Milan, Italy. *email:
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hospital rooms), the second one corresponds to the average concentration found in the sputum of COVID-19
infected patients, and the third one is a very large concentration, corresponding to that observed in terminally
diseased COVID-19 patients29. Aer UV-C exposure, viral replication was assessed by culturepolymerase chain
reaction (C-RTPCR) targeting two regions (N1 and N2) of the SARS-CoV-2 nucleocapsid gene, as well as by
analyzing SARS-CoV-2-induced cytopathic eect. Analyses were performed in the culture supernatant of infected
cells at three dierent time points (24, 48 and 72h for SARS-CoV-2 at MOI 1000 and 5; 24, 48h and 6days for
SARS-CoV-2 at MOI 0.05), as well as on cell lysates at the end of cellular culture (72h: MOI 1000 and 5; 6days:
MOI 0.05). is approach allows to follow the kinetic of viral growth and to verify whether the used dose is
sucient to completely inactivate the virus over time. is is useful from a practical point of view, when UV-C
devices are used to disinfect surfaces and the environment.
e eect of the UV-C exposure on SARS-CoV-2 replication was extremely evident and independent from
the MOI employed; dose–response and time-dependent curves were observed. Figures1, 2 and 3 report for dif-
ferent MOI the number of SARS-CoV-2 copies for the three concentrations as a function of the UV-C dose and
time, quantied on a standard curve from a plasmid control. e corresponding normalised curves of the virus
copies are reported in the same gures.
Viral replication was not observed at the lowest viral concentration (0.05 MOI) in either untreated or in UV-
C-irradiated samples in the initial 48h (Fig.1). However, 6days aer infection, viral replication was distinctly
evident in the UV-C unexposed condition, but was completely absent following UV-C irradiation even at 3.7mJ/
cm2 both in cell culture supernatants (Fig.1A,B) and in cell lysate (Fig.1C). A two-way ANOVA analysing the
eect of UV-C dose and time of incubation failed to identify a signicant eect of the UV exposure on viral
replication. is is due to the fact that at very low MOI relevant increases in N1 and N2 copy numbers were
detectable only in a single condition—at six days in the absence of UV-C exposure—thus hampering the statisti-
cal power of the analysis.
At the intermediate viral concentration (5 MOI), a signicant reduction of copy number starting from the
3.7mJ/cm2 dose with a decrease of a factor of 2000 (> 3-log decrease) aer 24h was observed (Fig.2D). A
two-way ANOVA conrmed that this UV-C dose signicantly dampened viral replication (p = 0.000796, and
p = 0.000713 for N1 and N2 copies respectively). Even more important, the copy number did not increase over
time, suggesting an eective inactivation of the virus, which was further conrmed by cytopathic eect assess-
ment (Fig.3A–C).
Using a high viral input (MOI = 1000), the two-way ANOVA conrmed that all the tree UV doses ana-
lysed resulted in a signicant suppression of viral replication for both N1 (3.7mJ/cm2: p = 0.008455; 16.9 mJ/
cm2: p = 0.004216; and 84.4mJ/cm2: p = 0.000202) and N2 copies (3.7mJ/cm2: p = 6.43E−05; 16.9 mJ/cm2:
p = 1.68E−05; and 84.4mJ/cm2: p = 1.68E−05) (Fig. 4). Notably, a dierent course of infection was observed,
in which the inhibitory eect was not accompanied by viral suppression for the UV-C dose of 3.7mJ/cm2
Figure1. Viral replication of UV-irradiated SARS-CoV-2 (0.05 MOI) virus in invitro VeroE6 cells. Vero
E6 cells were infected with UV-C irradiated SARS-CoV-2 virus at a MOI of 0.05. Culture supernatants were
harvested at the indicated times (24, 48h and 6days) and virus titers were measured (A,B) by absolute copy
number quantication (Real-Time PCR). Viral replication was assessed even on cell lysate harvested at the end
of cell cultures (6days) (C). All cell culture conditions were seeded in duplicate. Panel (D) reports the plots
of the measured virus copies normalized at the untreated sample in the dierent conditions. For descriptive
purposes, mean values and whiskers representing the observed half-ranges are shown.
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(Fig.4A,B,D). Indeed, a relevant reduction in N1 e N2 copy numbers was observed in a UV-C dose-dependent
manner as early as 24h (by a factor of 103 at 3.7mJ/cm2 and 104 at 16.9mJ/cm2, Fig.4A,B,D), but longer culture
times resulted in an increase in N1 and N2 copy numbers for the UV-C dose of 3.7mJ/cm2. is indicates that
the residual viral input le by the 3.7mJ/cm2 was able to replicate and sucient to generate an eective infection.
is is not the case in cultures exposed to higher UV-C doses, as no replication could be detected in these condi-
tions. All the results were further conrmed by 2-ANOVA statistical analyses performed on viral replication at
intracellular level (3.7mJ/cm2 vs. untreated: N1, p = 0.008455; N2: p = 6.43E−05; 16.9mJ/cm2 vs. untreated: N1,
p = 0.004216; N2: p = 1.68E−05; 84.4mJ/cm2 vs. untreated: N1, p = 0.004216; N2: p = 1.68E−05) (Figs.1C, 2C, 4C).
We compared our results with data available in the literature and observed that our inactivating dose is much
smaller than that reported in Heilingloh etal.26 (1000mJ/cm2 for the complete inactivation). is discrepancy is
likely to be the consequence of the UV-C absorption by the medium used in Heilingloh etal., which has a fourfold
higher thickness compared to the one used in our experiments. is possibility is supported by the observation
that 200mJ/cm2 of UV-A, which is not absorbed by the medium, was sucient to reduce viral replication of 1-log.
As UV-A light is signicantly less ecient (order of magnitudes) than UV-C, the reported UV-C inactivating
dose (100mJ/cm2) seems to be questionable.
Two other papers measured the eect of UV-C light on SARS-CoV-2. In Ruetalo etal.25, the illumination of
254nm light was employed on a dried sample of SARS-CoV-2. Complete inactivation was obtained with 20mJ/
cm2, a value greater than ours, but in the same range. It has to be underlined that in the dried lm a shielding
Figure2. Viral replication of UV-irradiated SARS-CoV-2 (5 MOI) virus in invitro VeroE6 cells. Vero E6 cells
were infected with UV-C irradiated SARS-CoV-2 virus at a MOI of 5. Culture supernatants were harvested at
the indicated times (24, 48 and 72h) and virus titers were measured by absolute copy number quantication
(Real-Time PCR, A,B). Viral replication was assessed even on cell lysate harvested at the end of cell cultures
(72h) (C). All cell culture conditions were seeded in duplicate. Panel (D) reports the plots of the measured virus
copies normalized at the untreated sample in the dierent conditions. For descriptive purposes, mean values and
whiskers representing the observed half-ranges are shown.
Figure3. Analyses of virus induced cytopathic eect. (A) No cytopathic eect was observed in uninfected
cultured VeroE6 monolayers maintained in 50mJ/cm2 UV-treated complete medium for 72h. (B) Invitro
infection of SARS-CoV-2 (5 MOI) UV-C untreated VeroE6 cells resulted in an evident cytopathic eect. (C)
SARS-CoV-2 irradiation with 3.7mJ/cm2 UV-C rescued the cytopathic eect induced by UV-C untreated virus.
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eect by the organic component present in the liquid can occur, reducing the eciency of the UV-C light. is
was shown by Ratnesar-Shumate etal.28, who demonstrated that the dose required to obtain a similar degree
of viral inactivation was twice in dried samples from gMEM compared to the ones resuspended in simulated
saliva. Notably, the two mediums dier for their composition, mainly in terms of protein and solid percentage,
with higher values for the gMEM.
Inagaki etal. used a 285nm UV LED and showed that a dose of about 38mJ/cm2 was sucient to com-
pletely inactivate SARS-CoV-2. is dose is greater compared to the one we established; this discrepancy can be
explained by the observation that the 285nm is less ecient than the 254nm wavelength24. Finally, in an elegant
study Storm etal.27 compared the virucidal eect of UV-C in wet and dry systems. Results were based on the
use of a very small volume of viral stock in DMEM (5μl) and showed that a dose of 3.4mJ/cm2 inactivated wet
samples, whereas a dose that twice as high was needed in dried samples. ese results are comparable to the ones
herein, and the shielding eect in dried samples is almost evident. Such comparisons show how the experimental
conditions adopted signicantly impact on the denition of the dose of UV-C resulting in virus inactivation.
It is therefore crucial to accurately describe all the details of the experiments to perform a reliable comparison.
In conclusion, we report the results of a highly controlled experimental model that allowed us to identify the
UV-C radiation dose sucient to inactivate SARS-CoV-2. e response depends on both the UV-C dose and
the virus concentration. Indeed, for virus concentrations typical of low-level contaminated closed environment
and sputum of COVID-19 infected patients, a very small dose of less than 4mJ/cm2 was enough to achieve full
inactivation of the virus. Even at the highest viral input concentration (1000 MOI), viral replication was totally
inactivated with a dose 16.9mJ/cm2. ese results show how the SARS-CoV-2 is extremely sensitive to UV-C
light and they are important to allow the proper design and development of ecient UV based disinfection
methods to contain SARS-CoV-2 infection.
In vitro SARS‑CoV‑2 infection assay. 3 × 105 VeroE6 cells were cultured in DMEM (ECB7501L, Euro-
clone, Milan, Italy) with 2% FBS medium, with 100 U/ml penicillin and 100μg/ml streptomycin, in a 24-well
plate one day before viral infection assay. SARS-CoV-2 (Virus Human 2019-nCoV strain 2019-nCoV/Italy-
INMI1, Rome, Italy) at a multiplicity of infection (MOI) of 1000, 5 and 0.05 were treated with dierent doses of
UV-C radiation (see the dedicated section) before inoculum into VeroE6 cells. UV-C-untreated virus served as
positive controls. Cell cultures were incubated with the virus inoculum in duplicate for three hours at 37°C and
5% CO2. en, cells were rinsed three times with warm PBS, replenished with the appropriate growth medium
and observed daily for cytopathic eect. Viral replication in culture supernatants was assessed by an Integrated
Culturepolymerase chain reaction (C-RTPCR) method30 at 24, 48, and 72h post-infection (hpi) while infected
cells were harvested for RNA collection at 72 hpi. Cell cultures from SARS-CoV-2 at 0.05 MOI were harvested
6days post infection. RNA was extracted from VeroE6 cell culture supernatant and cell lysate by the Maxwell
RSC Instrument with Maxwell RSC Viral Total Nucleic Acid Purication Kit (Promega, Fitchburg, WI, USA),
Figure4. Viral replication of UV-irradiated SARS-CoV-2 (1000 MOI) virus in invitro VeroE6 cells. Vero
E6 cells were infected with UV-C irradiated SARS-CoV-2 virus at a MOI of 1000. Culture supernatants were
harvested at the indicated times (24, 48 and 72h) and virus titers were measured (A,B) by absolute copy number
quantication (Real-Time PCR). Viral replication was assessed even on cell lysate harvested at the end of cell
cultures (72h) (C). All cell culture conditions were seeded in duplicate. Panel (D) reports the plots of the
measured virus copies normalized at the untreated sample in the dierent conditions. For descriptive purposes,
mean values and whiskers representing the observed half-ranges are shown.
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quantied by the Nanodrop 2000 Instrument (ermo Scientic) and puried from genomic DNA with RNase-
free DNase (RQ1 DNase; Promega). One microgram of RNA was reverse transcribed into rst-strand cDNA in
a 20-μl nal volume as previously described31,32.
Real-time PCR was performed on a CFX96 (Bio-Rad, CA, USA) using the 2019-nCoV CDC qPCR Probe
Assay emergency kit (IDT, Iowa, USA), which targets two regions (N1 and N2) of the nucleocapsid gene of
SARS-CoV-2. Reactions were performed according to the following thermal prole: initial denaturation (95°C,
10min) followed by 45 cycles of 15s at 95°C (denaturation) and 1min at 60°C (annealing-extension).
Viral copy quantication was assessed by creating a standard curve from the quantied 2019-nCoV_N posi-
tive Plasmid Control (IDT, Iowa, USA).
UV illumination test. e illumination of the virus solution was conducted using a low-pressure mercury
lamp mounted in a custom designed holder, which consist in a box with a circular aperture 50mm in diameter
placed at approximately 220mm from the source. e aperture works as a spatial lter to make the illumination
of the area behind more uniform. A mechanical shutter is also present to start the illumination process. e plate
is placed 30mm below the circular aperture and a single dwell (34.7mm in diameter), centered in respect to the
50mm aperture, has been irradiated from the top. e dwell was lled with 0.976ml of the virus suspended in
Dulbecco’s Modied Eagle’s Medium (DMEM) in order to have a 1mm thick liquid layer. Aer the irradiation,
the sample was treated as described in the previous section.
The intensity of the lamp and its spectral properties have been measured using an Ocean Optics
HR2000 + spectrometer (Ocean Optics Inc., Dunedin, USA). e HR2000 + spectrometer was calibrated against
a reference deuterium–halogen source (Ocean Optics Inc. Winter Park, Winter Park, Florida) and in compliance
with National Institute of Standards and Technology (NIST) practices recommended in NIST Handbook 150-2E,
Technical guide for Optical Radiation Measurements. e last calibration was performed in March 2019. e
detector of our spectrometer is a high-sensitivity 2048-element Charge-Coupled Device (CCD) array from Sony.
e spectral range is 200–1100nm with a 25μm wide entrance slit and an optical resolution of 1.4nm (FWHM).
e cosine-corrected irradiance probe, model CC-3-UV-T, is attached to the tip of a 1m long optical bre and
couples to the spectrometer. e intensity of the lamp has been measured by positioning the spectrometer in ve
positions: in the center and at the ends of a 20mm cross arm aer a warming up time of 30s. e spectra in the
ve positions are reported in Fig.5A together with a scheme of the dwell and illuminated area.
As expected, the emission is dominated by the UV-C line (Fig.5A) and its intensity was uniform in the area
with an average value of 1.082 mW/cm2. e stability of the lamp was evaluated in ± 11E−3mW/cm2 during a
130s measurement. According to this value, three exposure times were set: 5, 23 and 114s (with an accuracy of
0.2s), which correspond to following doses: 5.4, 25.0, 123.4mJ/cm2. is is the nominal UV doses provided to
the dwell, but we were interested in the eective doses (De) reaching the virus. It was necessary to calculate the
eective irradiance (Ie). is step was performed considering both the reection losses at the air/water interface
(Rw) and the Transmittance (Ts) of the DMEM solution at 254nm (from the spectrum in Fig.5B, considering the
cuvette losses, Ts = 0 0.70). It is important to notice that the spectrum was measured in a quartz cuvette (1mm
thick) by means of a Jasco V770 spectrophotometer and this thickness was the same of the solution in the dwell
during the UV irradiation step.
e reection loss was computed as follow:
where nw = 1.375 is the refractive index of water at 254nm. en, Ie was calculated:
Figure5. Mercury lamp spectrum measured in the ve positions (A). Inset: scheme of the illuminated dwell
and the measuring position. UV–vis transmission spectrum of the Dulbecco’s Modied Eagle’s Medium
(DMEM) in a 1mm quartz cuvette (B).
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e nal transmission of the DMEM solution was equal to 0.68 and the corresponding eective doses were
derived simply multiplying Ie by the exposure time.
According to this value, the eective doses provided to the viruses were: 3.7 ± 0.15, 16.9 ± 0.2 and 84.4 ± 0.9mJ/
cm2. We have to notice that we are neglecting here the absorption of the virus at this wavelength and the pos-
sible scattering. Such approximations are valid considering the relative low concentration of the virus and small
thickness of the layer (the solution appeared fully transparent).
Statistical analyses. To assess the eect of the dierent UV-C doses on N1 and N2 copy numbers, two-
way ANOVAs were performed. For the analysis of intracellular N1 and N2 doses in the supernatant, UV-C dose
and MOI represented the dependent variables, while for the analysis of N1 and N2 in the supernatant, dierent
analyses were performed for individual MOI, using UV-C dose and time as dependent variables.
Received: 3 July 2020; Accepted: 22 February 2021
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is research was partially supported by a grant from Falk Renewables and it has been carried out in the con-
text of the activities promoted by the Italian Government and in particular, by the Ministries of Health and of
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Scientic Reports | (2021) 11:6260 | 
University and Research, against the COVID-19 pandemic. Authors are grateful to INAF’s President, Prof. N.
D’Amico, for the support and for a critical reading of the manuscript.
Author contributions
P.G., L.L. E.R. and A.Z. designed and produced the illumination system; A.C., C.C. and M.L. performed the lamp
calibration; A.B. performed the lamp setup and lamp dosimetry, wrote the main manuscript; M.B. performed
biological experiments, analyzed the data, wrote the main manuscript; C.F., I.S. designed and performed some
biological tests; E.T, A.A. performed the statistical analysis; D.T. discussed the results; G.P. and M.C. supervised
the study and review the manuscript.
Competing interests
e authors declare no competing interests.
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... Recently, several studies have demonstrated the efficiency of the use of direct UV-C against the SARS-CoV-2 virus. According to [85], a small dose of UV-C irradiation (3.7 mJ/cm 2 ) is sufficient to inactivate COVID-19 in an indoor environment. Another study conducted by Vranay et al. [86] has shown that more than 90% of the SARS-CoV-2 virus can be inactivated by UV-C sources. ...
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... Physical methods for inhibiting the activity of SARS-CoV-2 include dry disinfection using thermal energy, light energy, or mechanical treatment [5]. Ultraviolet (UV) C (UVC) light with a wavelength of 200-280 nm (especially 254 nm) can destroy genetic materials, such as the RNA or deoxyribonucleic acid (DNA) in human cells, as well as pathogens, such as viruses, bacteria, and fungi [6]. Moreover, thermal energy can be used to inactivate SARS-CoV-2 by aging the protein surrounding the virus. ...
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Viruses and bacteria, which can rapidly spread through droplets and saliva, can have serious effects on people’s health. Viral activity is traditionally inhibited using chemical substances, such as alcohol or bleach, or physical methods, such as thermal energy or ultraviolet-light irradiation. However, such methods cannot be used in many applications because they have certain disadvantages, such as causing eye or skin injuries. Therefore, in the present study, the electrical stimulation method is used to stimulate a virus, namely, coronavirus 229E, and two types of bacteria, namely, Escherichia coli and Staphylococcus aureus, to efficiently reduce their infectivity of healthy cells (such as the Vero E6 cell in a viral activity-inhibition experiment). The infectivity effects of the aforementioned virus and bacteria were examined under varying values of different electrical stimulation parameters, such as the stimulation current, frequency, and total stimulation time. The experimental results indicate that the activity of coronavirus 229E is considerably inhibited through direct-current pulse stimulation with a current of 25 mA and a frequency of 2 or 20 Hz. In addition, E. coli activity was reduced by nearly 80% in 10 s through alternating-current pulse stimulation with a current of 50 mA and a frequency of 25 Hz. Moreover, a self-powered electrical stimulation device was constructed in this study. This device consists of a solar panel and battery to generate small currents with variable frequencies, which has advantages of self-powered and variable frequencies, and the device can be utilized on desks, chairs, or elevator buttons for the inhibition of viral and bacterial activities.
... SARS-CoV-2 0.9 3.2 6 PERT (Biasin et al., 2021;Heilingloh et al., 2020;Inagaki et al., 2020;Raeiszadeh and Adeli, 2020) performance of the 3 MLD STP was investigated using the midpoint approach for all 18 impact categories of the ReCiPe methodology, and the impacts are presented in Fig. 2. ...
An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.
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Sejak akhir 2019, virus SARS-CoV2 (severe acute respiratory syndrome – corona virus type 2) menyebar dengan cepat antar manusia, menyebabkan pandemi Covid-19 (corona virus disease 2019) yang membuat rumah sakit – rumah sakit di seluruh penjuru dunia kewalahan dan kematian pada sebagian pasien. Salah satu metode yang sering dipakai untuk mematikan virus yang menempel di permukaan benda adalah dengan radiasi UV. Seiring dengan maraknya produk-produk UV Sanitizer yang beredar di masyarakat untuk pemakaian rumah tangga, pengetahuan mengenai UV surface sanitation menjadi penting, baik dari sisi efektivitas germicidal (daya membunuh kuman), maupun keselamatan pengguna. Artikel ini membahas bagaimana UV digunakan untuk mendisinfeksi permukaan, dosis dan efek panjang gelombang yang digunakan, jenis-jenis lampu UV, serta aspek keselamatan dari penggunaan UV. Selain disinfeksi permukaan, disinggung juga sedikit UV untuk disinfeksi udara dan cairan.
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The COVID-19 pandemic has created an urgent need to utilize existing and develop new intervention technologies for SARS-CoV-2 inactivation on surfaces and in the air. Ultraviolet (UV) technology has been shown to be an effective antimicrobial intervention. Here a study was conducted to determine the efficacy of commercially available UV and blue light-based devices for inactivating HCoV-229E, a surrogate of SARS-CoV-2. The results indicate that two UV devices designed for surface disinfection, with doses of 8.07 µJ/cm² for the 254 nm device and 20.61 µJ/cm² for the 275 nm device, were efficient in inactivating 4.94 logs of surface inoculated HCoV-229E. Additionally, a 222 nm UV device with intended ceiling-based operation was effective in inactivating 1.7 logs of the virus inoculated on surface, with a dose of 6 mJ/cm². A ceiling-based device designed to emit blue light at 405 nm was found to produce 89% reduction in HCoV-229E inoculated on a surface for a dose of 78 J/cm². Finally, the UV based 222 nm device was found to produce a 90% reduction in the concentration of airborne HCoV-229E, at a 55 µJ/cm² dose. These results are indicative of the great potential of using UV based technology for the control of SARS-CoV-2. Implications: An important avenue of arresting COVID-19 and future pandemics caused by infectious pathogens is through environmental disinfection. To this effect, the study presented here evaluates commercially available UV and blue light based antimicrobial devices for their ability to kill the human coronavirus HCoV-229E, a surrogate of SARS-CoV-2, on surfaces and in air. The results indicate that two handheld UV devices produced complete inactivation of surface viral inoculum and a UVC ceiling based device produced 1 log reduction in HCoV-229E in air. These results imply the efficacy of UV technology as an antimicrobial tool, especially for rapid disinfection of indoor air.
COVID‐19 appeared in December 2019, needing efforts of science. Besides, a range of light therapies (PDT, Ultraviolet UV, Laser) has shown scientific alternatives to conventional decontamination therapies. METHODS: Investigating the efficacy of light‐based therapies for environment decontamination against SARS‐CoV2, a PRISMA systematic review of Phototherapies against SARS‐CoV or MERS‐CoV species discussing changes in viral RT‐PCR was done. After searching MEDLINE/PubMed, EMBASE, and LILACS we have found studies about cell cultures irradiation (18), blood components irradiation (10), N95 masks decontamination (03), inanimate surface decontamination (03), aerosols decontamination (03), hospital rooms irradiation (01) with PDT, LED, and UV therapy. The best quality results showed an effective low time and dose UV irradiation for environments and inanimate surfaces without human persons as long as the devices have safety elements dependent on the surfaces, viral charge, humidity, radiant exposure. To interpersonal contamination in humans, PDT or LED therapy seems very promising and are encouraged.
Monkeypox disease is caused by a virus which belongs to the orthopoxvirus genus of the poxviridae family. This disease has recently spread out to several non‐endemic countries. While some cases have been linked to travel from endemic regions, more recent infections are thought to have spread in the community without any travel links, raising the risks of a wider outbreak. This state of public health represents a highly unusual event which requires urgent surveillance. In this context, the opportunities and technological challenges of current bio/chemical sensors, nanomaterials, nanomaterial characterization instruments, and artificially intelligent biosystems collectively called “advanced analytical tools” are reviewed here, which will allow early detection, characterization, and inhibition of the monkeypox virus (MPXV) in the community and limit its expansion from endemic to pandemic. A summary of background information is also provided from biological and epidemiological perspective of monkeypox to support the scientific case for its holistic management using advanced analytical tools. The work discusses analytical technologies and presents opportunities & challenges to address the silent spread of monkeypox virus.
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Prolonged human-crewed missions on the Moon are foreseen as a gateway for Mars and asteroid colonisation in the next decades. Health risks related to long-time permanence in space have been partially investigated. Hazards due to airborne biological contaminants are possible. A possible way to perform pathogens' inactivation is by employing the shortest wavelength range of Solar ultraviolet radiation, the so-called germicidal range. On Earth, it is totally absorbed by the atmosphere and does not reach the surface. In space, such UV solar component is present and effective germicidal irradiation for airborne pathogens' inactivation can be achieved inside habitable outposts through a combination of highly reflective internal coating and optimised geometry of the air ducts. The Solar Ultraviolet Light Collector for Germicidal Irradiation on the Moon is a project whose aim is to collect Ultraviolet solar radiation and use it as a source to sanitise the re-circulating air of the human outposts. The most favourable positions where to place these collectors are over the peaks at the Moon's poles, which have the peculiarity of being exposed to solar radiation most of the time. On August 2022, NASA communicated to have identified 13 candidate landing regions near the lunar South Pole for Artemis missions. Another advantage of the Moon is its low inclination to the ecliptic, which maintains the Sun’s apparent altitude inside a reduced angular range. For this reason, Ultraviolet solar radiation can be collected through a simplified Sun's tracking collector or even a static collector and used to sanitise the recycled air. Fluid-dynamic and optical simulations have been performed to support the proposed idea. The expected inactivation rates for some airborne pathogens, either common or found on the International Space Station, are reported and compared with the proposed device efficiency. The results show that it is possible to use Ultraviolet solar radiation directly for air sanitation inside the lunar outposts and deliver a healthy living environment to the astronauts.
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Background Following two years of the Covid-19 pandemic, thousands of deaths were registered around the world. A question on whether climate parameters in each country could or not affect coronavirus incidence and Covid-19 death toll is under debate. Objective In this work, we aimed to analyse possible relation between the prevalence of Covid-19 deaths and the geographic latitude. The study focused on the geographic latitudes and some of their associated climate factors, such as the average annual level of temperature, sunshine hours and UV index. Methods We sought the deaths number caused by Covid-19 in 39 countries. Latitude levels were plotted against the average annual levels of either temperature, sunshine hours or UV index. Data was analysed by simple linear regression or polynomial regression, by mean of Microsoft Exell software (2016). Results When Covid-19 death numbers were plotted against geographic latitudes, we obtained inverted bell-shaped curves, for both the first and second year of the pandemic, with a coefficient of determination of (R ² = 0,32) and (R ² = 0,39), respectively. In addition, Covid-19 death numbers were very negatively correlated with the average annual levels of temperature (R ² = 0,52, P= 4.92x10 ⁻⁷ ), sunshine hours (R ² = 0,36, P= 7.68x10 ⁻⁶ ) and UV index (R ² = 0,38, P= 4.16x10 ⁻⁵ ). Bell-shaped curves were obtained when latitude was plotted against the average annual number of temperature, sunshine hours and UV index, with a coefficient of determination of (R ² = 0,85), (R ² = 0,452) and (R ² = 0,87), respectively. Conclusion In contrast to high latitude countries, countries located at low latitudes may have suffered less Covid-19 death tolls, thanks to their elevatd temperature, sunshine hours and UV index. The above climate factors, in addition to yet unknown factors, could have impaired the spread of the coronavirus, and/or helped individual’s natural immunity to fight Covid-19 disease.
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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has devastated global public health systems and economies, with over 52 million people infected, millions of jobs and businesses lost, and more than 1 million deaths recorded to date. Contact with surfaces contaminated with droplets generated by infected persons through exhaling, talking, coughing and sneezing is a major driver of SARS-CoV-2 transmission, with the virus being able to survive on surfaces for extended periods of time. To interrupt these chains of transmission, there is an urgent need for devices that can be deployed to inactivate the virus on both recently and existing contaminated surfaces. Here, we describe the inactivation of SARS-CoV-2 in both wet and dry format using radiation generated by a commercially available Signify ultraviolet (UV)-C light source at 254 nm. We show that for contaminated surfaces, only seconds of exposure is required for complete inactivation, allowing for easy implementation in decontamination workflows.
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Evidence has emerged that SARS-CoV-2, the coronavirus that causes COVID-19, can be transmitted airborne in aerosol particles as well as in larger droplets or by surface deposits. This minireview outlines the underlying aerosol science, making links to aerosol research in other disciplines. SARS-CoV-2 is emitted in aerosol form during normal breathing by both asymptomatic and symptomatic people, remaining viable with a half-life of up to about an hour during which air movement can carry it considerable distances, although it simultaneously disperses. The proportion of the droplet size distribution within the aerosol range depends on the sites of origin within the respiratory tract and on whether the distribution is presented on a number or volume basis. Evaporation and fragmentation reduce the size of the droplets, whereas coalescence increases the mean droplet size. Aerosol particles containing SARS-CoV-2 can also coalesce with pollution particulates, and infection rates correlate with pollution. The operation of ventilation systems in public buildings and transportation can create infection hazards via aerosols, but provides opportunities for reducing the risk of transmission in ways as simple as switching from recirculated to outside air. There are also opportunities to inactivate SARS-CoV-2 in aerosol form with sunlight or UV lamps. The efficiency of masks for blocking aerosol transmission depends strongly on how well they fit. Research areas that urgently need further experimentation include the basis for variation in droplet size distribution and viral load, including droplets emitted by “superspreader” individuals; the evolution of droplet sizes after emission, their interaction with pollutant aerosols and their dispersal by turbulence, which gives a different basis for social distancing.
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Background The SARS-CoV-2 pandemic urges for cheap, reliable, and rapid technologies for disinfection and decontamination. One frequently proposed method is UV-C irradiation. However, UV-C doses necessary to achieve inactivation of high-titer SARS-CoV-2 are poorly defined. Methods Using a box and two handheld systems designed to decontaminate objects and surfaces we evaluated the efficacy of 254 nm UV-C treatment to inactivate surface dried SARS-CoV-2. Results Drying for two hours did not have a major impact on the infectivity of SARS-CoV-2, indicating that exhaled virus in droplets or aerosols stays infectious on surfaces at least for a certain amount of time. Short exposure of high titer surface dried virus (3-5*10^6 IU/ml) with UV-C light (16 mJ/cm ² ) resulted in a total inactivation of SARS-CoV-2. Dose-dependency experiments revealed that 3.5 mJ/cm ² were still effective to achieve a > 6-log reduction in viral titers whereas 1.75 mJ/cm ² lowered infectivity only by one order of magnitude. Conclusions Our results demonstrate that SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation. Furthermore, the data reveal that the relationship between UV-C dose and log-viral titer reduction of surface residing SARS-CoV-2 is non-linear. In the context of UV-C-based technologies used to disinfect surfaces, our findings emphasize the necessity to assure sufficient and complete exposure of all relevant areas by integrated UV-C doses of at least 3.5 mJ/cm ² at 254 nm. Altogether, UV-C treatment is an effective non-chemical possibility to decontaminate surfaces from high-titer infectious SARS-CoV-2.
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The global health-threatening crisis from the COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights the scientific and engineering potentials of applying ultraviolet (UV) disinfection technologies for biocontaminated air and surfaces as the major media for disease transmission. Nowadays, various environmental public settings worldwide, from hospitals and health care facilities to shopping malls and airports, are considering implementation of UV disinfection devices for disinfection of frequently touched surfaces and circulating air streams. Moreover, the general public utilizes UV sterilization devices for various surfaces, from doorknobs and keypads to personal protective equipment, or air purification devices with an integrated UV disinfection technology. However, limited understanding of critical UV disinfection aspects can lead to improper use of this promising technology. In this work, fundamentals of UV disinfection phenomena are addressed; furthermore, the essential parameters and protocols to guarantee the efficacy of the UV sterilization process in a human-safe manner are systematically elaborated. In addition, the latest updates from the open literature on UV dose requirements for incremental log removal of SARS-CoV-2 are reviewed remarking the advancements and existing knowledge gaps. This study, along with the provided illustrations, will play an essential role in the design and fabrication of effective, reliable, and safe UV disinfection systems applicable to preventing viral contagion in the current COVID-19 pandemic, as well as potential future epidemics.
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As public health teams respond to the pandemic of coronavirus disease 2019 (COVID-19), containment and understanding of the modes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is of utmost important for policy making. During this time, governmental regulators have been instructing resident with a series of physical distancing measures. However, currently there is no agreement on the role of aerosol transmission for SARS-CoV-2 among public health organizations from different countries. To this end, we aimed to review the evidences of aerosol transmission of SARS-CoV-2. Serval studies support that aerosol transmission of SARS-CoV-2 is plausible, and the plausibility (weight of combined evidence) is 8 out of 9, which is similar to SARS. Precautionary control strategies should consider aerosol transmission for effective mitigation of SARS-CoV-2.
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The coronavirus SARS-CoV-2 pandemic became a global health burden. We determined the susceptibility of SARS-CoV-2 to irradiation with ultraviolet light. The virus was highly susceptible to ultraviolet light. A viral stock with a high infectious titer of 5 × 10⁶ TCID50/ml was completely inactivated by UVC irradiation after nine minutes of exposure. The UVC dose required for complete inactivation was 1048 mJ/cm². UVA exposure demonstrated only a weak effect on virus inactivation over 15 minutes. Hence, inactivation of SARS-CoV-2 by UVC irradiation constitutes a reliable method for disinfection purposes in health care facilities and for preparing SARS-CoV-2 material for research purpose.
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The spread of novel coronavirus disease 2019 (COVID-19) infections worldwide has raised concerns about the prevention and control of SARS-CoV-2. Devices that rapidly inactivate viruses can reduce the chance of infection through aerosols and contact transmission. This in vitro study demonstrated that irradiation with a deep ultraviolet light-emitting diode (DUV-LED) of 280 ±5 nm wavelength rapidly inactivates SARS-CoV-2 obtained from a COVID-19 patient. Development of devices equipped with DUV-LED is expected to prevent virus invasion through the air and after touching contaminated objects.
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Although the unprecedented efforts the world has been taking to control the spread of the human coronavirus disease (COVID-19) and its causative etiology [Severe Acute Respiratory Syndrome- Coronavirus-2 (SARS-CoV-2)], the number of confirmed cases has been increasing drastically. Therefore, there is an urgent need for devising more efficient preventive measures, to limit the spread of the infection until an effective treatment or vaccine is available. The preventive measures depend mainly on the understanding of the transmission routes of this virus, its environmental stability, and its persistence on common touch surfaces. Due to the very limited knowledge about SARS-CoV-2, we can speculate its stability in the light of previous studies conducted on other human and animal coronaviruses. In this review, we present the available data on the stability of coronaviruses (CoVs), including SARS-CoV-2, from previous reports to help understand its environmental survival. According to available data, possible airborne transmission of SARS-CoV-2 has been suggested. SARS-CoV-2 and other human and animal CoVs have remarkably short persistence on copper, latex, and surfaces with low porosity as compared to other surfaces like stainless steel, plastics, glass, and highly porous fabrics. It has also been reported that SARS-CoV-2 is associated with diarrhea and that it is shed in the feces of COVID-19 patients. Some CoVs show persistence in human excrement, sewage, and waters for a few days. These findings suggest a possible risk of fecal-oral, foodborne, and waterborne transmission of SARS-CoV-2 in developing countries that often use sewage-polluted waters in irrigation and have poor water treatment systems. CoVs survive longer in the environment at lower temperatures and lower relative humidity. It has been suggested that large numbers of COVID-19 cases are associated with cold and dry climates in temperate regions of the world and that seasonality of the virus spread is suspected.
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Previous studies have demonstrated that SARS-CoV-2 is stable on surfaces for extended periods under indoor conditions. In the present study, simulated sunlight rapidly inactivated SARS-CoV-2 suspended in either simulated saliva or culture media and dried on stainless steel coupons. Ninety percent of infectious virus was inactivated every 6.8 minutes in simulated saliva and every 14.3 minutes in culture media when exposed to simulated sunlight representative of the summer solstice at 40oN latitude at sea level on a clear day. Significant inactivation also occurred, albeit at a slower rate, under lower simulated sunlight levels. The present study provides the first evidence that sunlight may rapidly inactivate SARS-CoV-2 on surfaces, suggesting that persistence, and subsequently exposure risk, may vary significantly between indoor and outdoor environments. Additionally, these data indicate that natural sunlight may be effective as a disinfectant for contaminated non-porous materials.
Public health concerns such as multi- and extensive drug-resistant tuberculosis, bioterrorism, pandemic influenza, and severe acute respiratory syndrome have intensified efforts to prevent transmission of infections that are completely or partially airborne using environmental controls. One such control, ultraviolet germicidal irradiation (UVGI), has received renewed interest after decades of underutilization and neglect. With renewed interest, however, come renewed questions, especially regarding efficacy and safety. There is a long history of investigations concluding that, if used properly, UVGI can be safe and highly effective in disinfecting the air, thereby preventing transmission of a variety of airborne infections. Despite this long history, many infection control professionals are not familiar with the history of UVGI and how it has, and has not, been used safely and effectively. This article reviews that history of UVGI for air disinfection, starting with its biological basis, moving to its application in the real world, and ending with its current status.