UV in the Age of COVID-19

Since the COVID-19 pandemic began spreading in the United States, ECRI has received an influx of questions about disinfection technologies. One such technology is ultraviolet (UV) disinfection systems—devices that use light from the UV spectrum to disinfect surfaces or air.

ECRI's Evaluations of two different UV disinfection device configurations—movable towers used for room disinfection and countertop models designed to disinfect tablets, phones, and other small devices—show that UV light can effectively reduce bioburden on surfaces. (The devices we've tested use 254 nm light.) With respect to SARS-CoV-2 in particular, experts expect its response will be similar to that of other coronaviruses, like SARS-CoV-1 and MERS-CoV, which have been shown to be inactivated by UV light. But proper use is key. The recommendations outlined below will help healthcare facilities make the most effective use of UV technology.
 

Disinfecting with UV Light

At the right wavelengths and with an appropriate exposure time, UV energy can disrupt the DNA or RNA of microorganisms that are exposed to the light, preventing them from replicating. Studies indicate that sufficient exposure to UV light can inactivate a wide range of microbes, including common strains found in hospitals, like methicillin-resistant Staphylococcus aureus (MRSA), Clostridioides difficile (C. diff), and vancomycin-resistant enterococci (VRE). Most UV disinfection devices use UVC light—that is, light within the 200-280 nm range—although some systems use UVB or far-UV wavelengths. In particular, UVC light at 254 nm has been well studied and is the most commonly used wavelength.

Within a healthcare facility, the technology may be applied in various ways:

• Room disinfection devices typically consist of a movable tower that houses mercury or xenon lamps that emit UV light. The devices may be placed in patient rooms, bathrooms, ORs, procedure rooms, or other locations following cleaning to help fight environmental contamination. Depending on the system, the tower (or towers) may remain in one location during the disinfection cycle, or the cycle may be paused and the device repositioned midway through the treatment period.
• Countertop models are smaller, enclosed devices that are typically used to disinfect mobile devices such as phones or tablets—items that may be susceptible to damage by chemical disinfection methods. Users first clean the surface of the item to remove debris; then they place it in the UV device and initiate the disinfection cycle.
• Additional designs include wall- or ceiling-mounted systems, systems designed for use in air-handling units, and other configurations.

When used properly and as a supplement to normal cleaning and disinfection processes, UV disinfection can be effective at reducing the environmental bioburden in a facility. However, UV disinfection technology may be less effective, or on occasion even dangerous, if not used properly.

During the COVID-19 pandemic, it has been suggested that UV disinfection units could be used to disinfect N95 respirators to help address personal protective equipment (PPE) shortages. ECRI considers that approach acceptable in limited reuse situations, but cautions that UV disinfection could:

1. Be ineffective at successfully deactivating pathogens located deep within the layers of filter material

2. Be limited by shadowing due to the geometry of the respirator

3. Damage the respirator in a way that reduces its effectiveness, such as by degrading the elasticity of the strap that secures the mask to the wearer

Research in this area is evolving rapidly, however, and recommendations may change.
 

8 Things to Know about UV Disinfection

The safe and effective use of UV disinfection devices requires a clear understanding of what the technology can and can't do. ECRI believes that the following points are essential for effective implementation:

1. UV disinfection is a supplement; cleaning and other practices should take precedence.

a) UV disinfection is not a requirement—thus there's no need to purchase a system if you don't already have one—and it is not a stand-alone solution that can address all your disinfection needs. If UV technology is to be used, be sure to use it in accordance with manufacturer recommendations and best practices.

b) Proper cleaning of surfaces and equipment is required regardless of whether UV is used. Solid particles and residues can protect microbes from UV light.

c) Proper hand hygiene and PPE use still must be observed, as recommended by U.S. Centers for Disease Control and Prevention (CDC) and other guidelines. UV light has the potential to reduce reservoirs of environmental pathogens, but it does not prevent pathogens from being reintroduced by direct contact, droplets, or air movement.

2. UV offers disinfection for noncritical items, not sterilization. UV doses have been validated to achieve a greater than 4-log reduction of common organisms, including bacterial spores. However, it has not been shown to eliminate microorganisms to the degree required for critical or semicritical items that will contact sterile, vascular, or mucous tissues. Countertop UV disinfecting devices, for example, cannot be used to sterilize materials such as surgical supplies or devices.

3. Line of sight is key. Surfaces that are not in a direct line of sight from the UV source may not be exposed to sufficient UV light and will not be reliably disinfected, unless steps are taken to increase exposure. For room disinfection applications, commonly shadowed surfaces include the undersides of tables, the backs of devices and door handles, and low areas such as under beds or chairs.

4. System settings and device positioning make a difference. The germicidal effectiveness of a system is related to the dose of UV light incident on a surface. That depends on factors such as the output of the UV device, the distance from the light source, the wavelength emitted, and the exposure time.

5. UV may not reliably disinfect fabrics, the inside of tubing, or other materials. UV disinfection has not been proven to be effective on fabrics, like privacy curtains. Additionally, UV doesn't penetrate through most materials, including plastics, even if they are clear or translucent. Thus, the lumens of clear plastic tubing won't receive an effective dose. The same can be true of the nooks and crannies on devices. Just because a device or object has been exposed to UV, that doesn't mean it's been effectively disinfected.

6. UV light can harm patients and staff. Safety precautions are needed to limit human exposure to UV light, which can damage an individual's eyes or skin. To reduce the risk, many UV room disinfection devices require the use of door or motion sensors that terminate the disinfection cycle if triggered, and manufacturers may recommend the use of signs outside the treatment room.

7. UV light can damage certain equipment. UV light breaks down certain materials over time. The degree of damage depends on the cumulative dose of UV and the type of material. Damage occurs more quickly for certain plastics and organic materials and if treatment cycles deliver higher UV doses or are performed more frequently.

8. UV disinfection systems are not regulated as medical devices. UV disinfection systems are not classified as medical devices and thus are not regulated by FDA. Further, there are no standardized test methods for comparing systems. Thus, facilities should regard manufacturer claims critically: Be sure to read the fine print, and look for citations that provide study details.