Can UVC LED deep ultraviolet disinfection lamps kill the novel coronavirus?
Can UVC LEDs (deep ultraviolet germicidal lamps) kill the novel coronavirus?
Let’s look at the coronavirus first. Coronaviruses are protein-enveloped, single-stranded, positive-sense RNA viruses. Previously, six types of coronaviruses were known to infect humans: α (229E, NL63) and β (OC43, HKU1, MERS-CoV and SARS-CoV). Of these, HKU1, MERSr-CoV and SARSr-CoV can cause pneumonia. The most well-known outbreaks were SARS in 2003 and MERS in 2012. Let’s look at the coronavirus first. Coronaviruses are protein-enveloped, single-stranded, positive-sense RNA viruses. To date, six coronaviruses are known to infect humans: those of the α genus (229E, NL63) and the β genus (OC43, HKU1, MERSr-CoV and SARSr-CoV). Of these, HKU1, MERSr-CoV and SARSr-CoV can all cause pneumonia. The most widely recognised are the 2003 Severe Acute Respiratory Syndrome (SARS) and the 2012 Middle East Respiratory Syndrome (MERS).
In terms of the strength of the virus’s binding to its receptor, the novel coronavirus 2019-nCoV has a weaker binding capacity than SARS-CoV; this suggests that its transmissibility may be lower than that of SARS, and that the structure of its binding domain is more susceptible to disruption, making it easier to control.
Research has found that the SARS virus is sensitive to thermal radiation and UVC. When the SARS virus is exposed to UVC irradiation at an intensity greater than 90 μW/cm², it can be inactivated within 30 minutes. Through laboratory simulations of the virucidal capacity of ultraviolet radiation in natural sunlight, it was found that under clear skies in Beijing at 10.00 am in May—that is, when UV intensity ranges from 4 μW to 5 μW/cm²—coronaviruses can be inactivated in vitro within three hours.
Furthermore, the survival of coronaviruses decreases significantly as the temperature rises. Under serum-free culture conditions, heating to 75°C for 30 minutes is sufficient to inactivate coronaviruses. Recent thermal inactivation experiments on 2019-nCoV have found that the virus can be inactivated within 30 minutes at a temperature of 56°C. Consequently, the UVC radiation dose required to inactivate 2019-nCoV may be lower than that required for SARS-CoV, although the exact dose requires further research to confirm.
In summary, when used in conjunction with other protective measures, UVC can, to a certain extent, effectively help to prevent and control the spread of the 2019-nCoV outbreak.
Based on known effective germicidal wavelengths, we have developed UVC chips in a variety of sizes, as well as small, medium, large and ultra-high-power UVC LED products. These have successfully passed validation testing and have been adopted by a number of renowned domestic and international brand clients, with applications spanning surface disinfection, disinfection of moving and static water bodies, and air purification and disinfection equipment.
How can UV LEDs be used for sterilisation and disinfection in the fight against the novel coronavirus?
UV light is effective for sterilisation and disinfection, but one should not rely solely on it. The primary mechanism of UV sterilisation and disinfection is protein inactivation, and this applies mainly to UVC products. Such applications are suitable for use on surfaces.
Research indicates that UV disinfection primarily achieves its effect by causing radiation damage to microorganisms and disrupting the function of their nucleic acids, thereby killing them. The action of UV on nucleic acids can lead to bond and strand breaks, interstrand cross-links and the formation of photochemical products, which alter biological activity and result in inactivation. With regard to viruses, these are primarily divided into two categories: DNA-based and RNA-based. DNA-based viruses are more stable due to their double-stranded structure, whereas RNA-based viruses, with their single-stranded structure, are relatively less stable and have a higher likelihood of mutation. Consequently, RNA-based viruses are more difficult to treat, and their variants and adaptability may be more complex.
Most viruses capable of infecting the human body are encased in a protein shell, which they use to deceive the body’s immune system and invade cells. The first stage of UVC’s action on viruses is to destroy this protective shell, causing the virus to lose its protective covering and rendering it unable to invade cells. Secondly, the DNA or RNA within the virus is also destroyed, thereby completely inactivating the virus. However, particular care must be taken with regard to the emergence of viral variants, to avoid selecting for stronger viruses during the disinfection process.
Looking to the future, with the Minamata Convention coming into force, UV LEDs still face challenges in terms of cost and energy efficiency. We are confident that, with technological progress and industrial development, these issues will be gradually addressed and overcome. As a more convenient, hygienic and environmentally friendly method of disinfection and sterilisation, UV LEDs will see increasing application. At the same time, as changes are made to packaging and power supply solutions—such as in terms of size—there will be significant breakthroughs in application scenarios such as foldable toothbrushes and concealed door handles. This is particularly true for applications in public spaces, which will be highly beneficial for external disinfection and sterilisation, and will greatly help to reduce and prevent the spread and proliferation of viruses and bacteria.
What UVC LED products are currently available for use in epidemic prevention and control?
According to the newly published *Rapid Guidelines for the Diagnosis and Treatment of Novel Coronavirus Pneumonia*, 75% alcohol, diethyl ether, chloroform, formaldehyde, chlorine-based disinfectants, peracetic acid and ultraviolet light can all inactivate the virus.
To date, over 5,000 UV disinfection units have been delivered to the Leishenshan and Huoshenshan Hospitals. It is reported that the first batch of UV disinfection units comprised hundreds of disinfection vehicles and over a thousand UV disinfection lamps; the disinfection vehicles will be used to transport patients, whilst the UV disinfection lamps can be utilised in various post-operative disinfection scenarios.
During this pandemic, in addition to UV disinfection vehicles and lamps being deployed directly at the scenes of the outbreak, many members of the public have also purchased mercury-based UV lamps for indoor disinfection, as well as using UV lamps to disinfect face masks in order to extend their lifespan.
It is widely recognised within the industry that ultraviolet lamps can disinfect and sterilise, but can they truly eliminate the novel coronavirus? What roles can current and future mercury-based UV lamps and deep-ultraviolet LEDs (UVC LEDs) play, respectively? Which UVC LED products can be used for sterilisation and disinfection to support the current epidemic prevention and control efforts? Experts in the UV LED sector and representatives from relevant organisations have provided their analysis on these points.
Deep ultraviolet LEDs (UVC LEDs) primarily achieve disinfection by utilising the 200 nm–280 nm wavelength range to cause radiation damage to microorganisms (such as bacteria, viruses and spores) and to destroy their nucleic acids, thereby killing them. Although UVC LEDs are currently still in their infancy, and their cost-effectiveness and luminous efficiency still fall short of those of mercury lamps, UVC LEDs, however, have already found widespread application in portable surface disinfection, the maternal and infant care market, and static water treatment, thanks to their safety, environmental friendliness, compact size, high efficiency, low energy consumption and the fact that they leave no chemical residues.
Health and hygiene standards in public spaces and for everyday household items are constantly rising, and UVC LEDs can play a significant role in this area. For example, in a project where Guoxing UVC LEDs were used in collaboration with a renowned international home appliance manufacturer to develop a humidifier, the application of UVC LED modules in the device prevented the growth of bacteria in water left standing for long periods, thereby ensuring a hygienic home environment. At the same time, there are numerous portable UVC LED sterilisation and disinfection products available for everyday items such as tableware and nappy bags. In hospitals, items used by medical staff—such as infrared thermometers, stethoscopes, blood pressure cuffs, mobile phones and spectacles—can also be disinfected using UVC LED sterilisers.
At present, for portable sterilisation devices and small household appliance sterilisers, the UVC LED’s light power, exposure time and beam angle vary depending on the specific usage environment. For example, in the case of some compact, portable sterilisation devices—which are primarily used on items that come into frequent contact with us in daily life, such as mobile phones and cutlery— for these, irradiation with a low-power UVC LED (2–5 mW) for a few seconds to several tens of seconds prior to use is sufficient; whereas for sterilising water cups, due to their slender structure, the UVC LEDs must be designed with a beam angle of 60 or 30 degrees to ensure a longer irradiation distance, whilst also accounting for the attenuation of the UVC spectrum in water; such products generally utilise units with a light output of around 10 mW; Furthermore, in low-flow water dispensers, the light output generally needs to be 50–100 mW or even higher. However, as higher power output leads to higher costs, some manufacturers currently combine centralised filtration and disinfection methods, installing UVC LED disinfection modules only at the final stage of the water outlet; this significantly reduces costs.
Therefore, from a purely current perspective, mercury-based UV lamps remain the primary technology used in water treatment, industrial sterilisation, hospital sterilisation and indoor sterilisation, whilst UV-C LEDs can play a significant role in household appliances and portable sterilisation and disinfection devices, which will be highly beneficial in reducing and containing the spread of viruses and bacteria in the home and in public places.
As mercury lamps gradually fade into history, UVC LEDs will continue to evolve towards higher power and greater luminous efficacy, whilst their wavelengths will continue to shift towards the lower end of the spectrum. This places greater demands on the packaging of UVC LEDs, and further improving heat dissipation and UV resistance will be a key challenge.
We believe that, when combined with other protective measures, UVC can, to a certain extent, effectively prevent and control the spread of the 2019-nCoV outbreak. Guoxing Optoelectronics will also work alongside the entire UVC LED industry chain to accelerate trials and research into the sterilisation of the novel coronavirus using ultraviolet irradiation.
